1st: If making a Covenant of helping players, just keep it as the Sunbroes, and let them be rewarded for both repelling invaders, and helping kill a boss. (Or surviving a allotted summon time.)
2nd: Revert the armor system to Dark Souls 1 style. Having different weight roll speeds and stamina usage clear and different helped add to the feel of the game. Light mages who didn't wear much were different then med armor dex guys who could roll okay but liked to bleed dudes out.
3rd: Fuck the adaptability stat thing. Having to put points in a stat to make your roll worth a damn was just bad, same thing with interacting with objects.
4th: Again, be like Dark Souls 1 and have interesting NPCs. Dark Souls 2 was mostly devoid of interesting characters I could care about. There was no sad boss relative who I could care about (Qualana's sister). Hex Ornstein had nothing explaining him or anything about him in the game. There was no charmingly creepy and helpful Solaire. (And the girl from DKS 2 just fucking disappears for no reason. At least Iron Tarkus had a corpse.)
5th: More sensible Covenants and locations. Seriously, this no name joker being the leader of the Dragon Covenant when there is a fucking ancient dragon in the game? Are you kidding me? Not even that, he's protected by fucking Covenant member NPCs!? More-so then that, we had to grab a item to give to said unimportant joker who has no affiliation for them? C'mon.
6th: Don't fucking lie to us about DLC. Moreso, don't fucking hold the rest of the campaign in DLC without at least telling us. And don't hold the best damned levels and story telling environments in the DLC.
7th: I don't mind the super 4 big bad gimmick we have. It's fun, but don't make them stupid re-hashed essentialy remakes/mind controlled by the old big bads, it just diminishes things.
8th: No enemies on top of bonfires pls, and while we're here, if we don't have a safe bonfire going to a npc or merchant who does something no one else can, you've kind of fucked up.
9th: If you have to do call back gear, do the characters who are neat, or kind of matter that adds to the lore. The black knight stuff, onionbro and havel gear just stood out as odd and misplaced amongst everything.
10th: Guarantee drops from enemies who only have one life. If I find all the secret dudes and hit them hard enough to drop them, and don't get their super limited drops, that's just aggravating.
11th: Better punching weapons pls. Better punching backstab/riposte animations please.
12th: This is something from Bloodborne, but criticals on bosses that are badass. Being able to stop a monolith and throw it down with a crit takes some skill and is very rewarding.
13th: More NPC invaders with a story, like Kirk. Also, more npc invaders who play tricks on players, like guy in frozen place who follows you in a box. And, well, more NPC invaders who are kind of special, like say in a area, you'll get invaded by the bosses 'guardians', kind of like the belltower, but not as frickin' assinine.
14th: A covenant less PVP gladiatorial arena, that changes a bit. (Like water flows in to slow movement, or poison fog fills in to damage both players, or another fog that negates all healing items.) This would be amazing, and let players just duke it out without needing items, and make it a special location of it's own. Even if there are PVP covenants, keep these here anyways as places where they can gather and have sweet combat at will.
15th: No forced invasion/summon area's. They're just pointless if you play offline, and more then likely annoying if you're playing online. And if you have to do them, which actually is fine, don't make them story forced where you have to go through them. Let players know what they are stepping into, and let them have a actual reward instead of just.. beating no body rat mans.
16th: Improved magic system. Power spells and built in aiming were good idea's, and did not need to be scrapped. More so, don't nerf this shit into the dirt, and get rid of the dual stat/uses lower deal that hexes had. More so, have a few special items/spells that let mages/swordsages to do close up combat properly. Actually, this is one place where you could have dual stats/use lower to make sure they're not a bit much.
17th: No soul memory. Maybe some kind of scaling system for the invaded/summoning player.
18th: It's own story and lore. Of course, it's in the Dark Souls continuity, but let's have it be able to stand on it's own merits unlike Dark Souls 2. So, let things add onto the lore, like more natural progressions of the covenants, kingdoms and aspects like Chaos and the Abyss.
There's more but kinda tired and yeah.