I'm going to buy FF13 but I thoroughly agree with you, I feel the following.
FF12 was a good attempt at revising the series. It had a more serious story, more realistic characters (at times) and a new take on an old battle system. It also had one of the BEST worlds we've ever seen however it also had a few glaring flaws that need addressing...
1) The world does not want Vaan or Tidus again, deal with it, I'd rather have Balthier or Zidane.
2) Give us USEFUL abilities, FFXII suffered from the fact that you never needed to do anything. Most Technicks were useless and I often only used magic when I needed the range. Also later boss battles were basically just Mist Knack festivals.
3) Story focus IS YOUR STRONG POINT, FFXII was too thin on plot and too heavy on the dungeon crawl.
4) Give us some Out of Combat play that isn't just "Run Around Village" or "Play Mini-Game A" and maybe integrating some sort of Out of Battle Skill System might be a good plan.
5) Pull Nomura from the series, his age is OVER, leave him with Kingdom Hearts and TWEWY, he did better there.
That's my opinion anyway. I don't feel that the Final Fantasy series should transform into WRPG's, I don't want to see creatable heros with no personality, I don't care if its linear or non-linear, I don't want to see the series descend into crappy realtime battles ala Star Ocean or Tales Games.