(OK, this is going to be a long one. If you're interested, buckle up.)
Well the levelling needed some massive changes. And I like most of the changes. But what about the worst part of the whole thing, the random encounters?
"Ooh, this is lovely countryside. So much to gather! So much to explore! Dammit, I'm being attacked by a wolf. Ok, it's dead. Let's explore some more... damn, another wolf. WHAT THE HELL AM I, BLOODY PEST CONTROL?!?!!"
Get rid of random encounters. Replace them with specific areas or settlements where you can meet enemies of certain strengths, REGARDLESS of your levelling. In other words, if you wander into "The Cave of Nasty Little Lurking Goblins", expect to collect a few goblin skulls. If you happen upon "The Forest of Massive Minotaurs Wielding Iron Dildos of Death", you better be ready for a BIG fight. If, on the other hand, you want to go to "The Lake of Serene Beauty With Loads of Tasty Stuff to Gather For Alchemy", you can do that without being attacked by freaking wolves every two seconds. Sorted!
Plus the roads should be safer than the middle of the dark wood (obviously). But not too safe. There could still be "ambush spots" - again, specific areas where you MAY be attacked, that the locals might warn you about. Enemies could act more intelligently, waiting in cover until you reach a certain point, depending on the enemy type. They might attack a lone player but not when a guard is within sight.
And getting past them would require STRATEGY. Not just happening on one of a dozen monstrosities that all attack on sight anyway. Enemies might have different tactics, different levels of intelligence. Some ambush, some attack on sight. Some might be persuaded to negotiate to a non-violent solution. Some only fight to the end, but are easier to evade, etc. It might be better to pay off a big group of bandits using a bartering skill than try to outfight them using a combat one.
There should be alternatives to combat, but when combat is used, it should require strategy - sometimes it would be better to sit back and snipe with magic / ranged weapons, at other times you'd want to rush in using the element of surprise. And why is combat always the most important skill anyway? Sure, there'd be times when you'd HAVE to use it. But there should be alternatives for most encounters.
And the same might apply to NPC allies. "Oblivion"'s NPCs were annoying because they would always spoil any stealth or magic attacks by just running in and slashing at the nearest enemy. And if they happened to die but were mission-essential... well, let's just say, it wasn't much fun. What if you can order the NPC with a bow to only use ranged attacks, or concentrate on using specific magic types - for example, long-range attacks, conjuration, or healing/strengthening of companions? What if you could order a warrior NPC to act as "rearguard" and keep the other NPCs safe or watch your back?
Seriously... no wolves. No bloatflies. No radscorpions. No wild boars. And ESPECIALLY no giant rats. Let's get rid of random encounters, once and for all. They're not hard. They're not satisfying. They're not fun. They're a huge waste of time and energy. NOBODY wants to do them. There's enough to do in "Oblivion" without them, and I don't doubt the same will be true of Skyrim. So why include them?
Oh, and how about making the characters in the nearby settlements give the player information about what to expect? So the whole exploration thing becomes a little more structured - less "wander all over the countryside meeting the same enemy every few yards" and more "scout at the local inn to find out what kind of hulking monstorosity awaits in the valley past the next hill".
Oh... and if you clear a place, it stays clear for a decent amount of time. (So you don't clear a place of bandits, sleep at the inn, come back and find it full of bandits again.) Maybe, by clearing out a particular habitat, you can suggest at nearby settlements that friendly people set up settlements there. So instead of bandits, you meet friendlies. But then, after a set amount of time, they could be raided, pushed out, and replaced by monsters again.
Hell, maybe there could be dialogue about this specific outcome at the nearby settlements after a certain amount of time. Maybe you could actually tell people what you'd done rather than having to respond to their cues every time (eg "I took out the goblins in Hunters Wood earlier on, you guys want to go see if you can set up shop over there?") I mean, what's the point in speechcraft or negotiation skills if you can't use them to convince people to follow you or act in ways that are best for you or themselves? The player should be able to change his surroundings for the better, have an effect on the world he's playing in.
Oh, and finally, when you level skills, let's SEE those skills being levelled. Levelling speed makes you faster, acrobatics makes you jump visibly higher. Levelling swordsmanship causes your sword to swing faster so the power stays the same but you get more shots in a shorter amount of time. Levelling blunt weapons makes them swing harder (maybe increase the length of the swing), so you get the same amount of swings but they do visibly more damage and are more likely to stagger your enemies. Weapons do damage - they can cripple and decapitate if used properly. Bows fire arrows faster and, when drawn, the string is visibly further back. Spells are visibly larger and have greater area of effect. Etc, etc.
But the levelling shouldn't be overwhelming. A level 100 swordsman wields his blade one and a half times as fast as a level 20 swordsman, not eighty times as fast. "Levelling" shouldn't be the be-all and end-all of what you can do in the game - it should just be nice to be able to get the extra boost to your skills.
So that's my wishlist for Skyrim.
1) No random encounters - replace them with "set" encounters that are more difficult in wilder areas, like Evergreen Mills from "Fallout 3". Encounters should be large enough that you're forced to use strategy, and most of them should have a non-combat-based solution (eg stealth, negotiation). Once you clear out an area, it stays cleared out for a LONG time, so you don't have to do the same thing over and over again.
2) No levelling enemies. Have harder enemies in the later "quest" stages and in the middle of dark wooded areas, etc. So if you want to wander into those areas at low level, it's your own damn fault. A truly immersive world is one that doesn't SEEM to revolve around one person, the player, within it.
3) Enemies have different tactics other than "attack at range", "attack with magic" or "run and attack". They may run away if wounded, they may be willing to negotiate if faced with a show of strength. A lone wolf won't attack an armoured human being, but it might howl to summon its mates. (Can you imagine how creepy that might be?) Imperceptive or distracted enemies can be evaded with stealth. Enemies might have different levels of vulnerability to different magic or weapons that the player can exploit. Each battle should be tactical. There should be no such thing as repetition.
3) More situational dialogue. You can tell friendly people nearby if you've cleared out a mine or a ruin so they can go in and inhabit it. The player should be able to instigate dialogue, not just respond to topics introduced by others about quests, etc. The player shouldn't be the "chosen one", sent hither and fro at the whims of others to fulfil his inevitable destiny that everybody in the game knows about beforehand. He should be able to genuinely change his surroundings, if not the main storyline. (Actually a many-branched storyline would be fantastic, but it would also be pretty much impossible to pull off.)
4) More control over NPCs. If I want a party consisting of a strong warrior who'll watch my back, a priest who'll focus only on healing, a conjurer who keeps pressure on with summoned creatures and a ranger who attacks at range only, I can have it. If I want my mission-critical companion to stay out of combat and hide while I take on a group of enemies alone, I want to be able to tell them to do THAT as well. It's my damn game!
5) If I level up my skill wielding a sword, it slashes things visibly faster. If I level up my warhammer skill, it wallops things visibly harder. As I level up, I should develop more moves and my combat should have more visible effects. No more fighting plastic mannequins, I want to cripple, main and decapitate. That applies to every skill in the game. Don't just tell me, by way of spreadsheets, that I'm hitting enemies harder, jumping higher, or running faster. Let me see and hear the effects.
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Damn, that was LONG. Hopefully the developers of "The Elder Scrolls 6" read it, it's probably a little too late for "TES5"... I'm tempted to send it to 'em.