Reading through most of the ideas in the past 178 Threads I have noticed that the majority are "nice to haves". The real "must haves" in my opinion are:
1. overhauled combat system (mount & blade in 3D, 7.1 Digital Surround Sound, on Speed with a side order of steroids) http://www.gamesas.com/index.php?/topic/1113609-a-whole-new-combat-style-would-this-be-possible/page__p__16339990entry16339990
2. companion NPC's and creatures (pets), mounts, mounted combat, beasts of burden http://www.gamesas.com/index.php?app=forums&module=forums§ion=findpost&pid=16340357
3. overhauled armor system http://www.gamesas.com/index.php?/topic/1111409-tes-v-ideas-and-suggestions-175/page__st__120__p__16305297entry16305297
4. discoverable main quest and quests given based on faction reputation
5. overhauled stealth, sneak and guard/watchman system
The rest I don't really mind so much...
some ok sugestions
1. I really like the idea of training/specializing different combat styles. This is, in a way, already implemented. At least the idea of it is totally in tune. simply by specializing in any of the major weapon skills. but imo, the jump from MW and condensing some of the weapon skills in Ob was a backward step. I would be quite happy if they reintroduced more weapon skills, and maybe further expanded it to include styles. I think it's possible to do something with this idea.
2. summons and pets/beasts of burden are already in existance. horses, pack guars, that mini imp pet in one of the mages guild, hell even dogmeat or other companions in fallout, could be an indicator that this is likely to happen. I think further expanding this concept for pets is an interesting one.
3. i basically completely disagree here. While the slot system will probably return in some form, it will not be as you hope, the layering you are suggesting would be right bloody pita to complete seamlessly, when you are trying to get 20 outfits to be so interchangeable and not look like doodoo, its getting bonkers territory. but actually it's not out of the question.
as is the head/face slots will likely be face more accommodating than you expect, giving head, hat, eyeglasses, mask, and maybe several other slots, ala fallout. there maybe a complex form of 'armor addons' though. depends on a few factors, optimization and time constraints, + how awesome the designer of the system is. from modding F3 for a year, i can tell you it is very versatile if used correctly. I have a doubt separate pauldrons will make a return tbh. But at least they will probably get their own bones for rigging. I also doubt separate arm, sabatons I expect a mix of fallout3 and oblivion slot systems. but more F3 style. I
4&5 I can agree with. guards in Ob are fail. and anything that makes factions interesting.playable is worth while. the capes/robes may get a couple bones of their own too.
here is my suggestion
body types. basically facegen for the body. you gave us facial hair, now we need a fat norse bartender to serve us greef