The first I have been wondering about the system is how perks work in there, are they what I hope them to be as "sub-skills" or fancy new moves à la Oblivion? Or both? I'd lean towards the later. So perks would obviously work a lot different than in Oblivion, in order for the system to be a minimum deep and complex it would need to have a great number of them which can be levelled multiple of time, well more or less. I'd say there'd be several "tiers" of perks. But first off, let me start with an example.
Let's say that all the weapons/combat skills other than Marksman and Hand to Hand are fused into a single "Melee" skill. Nonsense you tell me, how can someone be as good with a knife, a claymore or a warhammer? Normally they can't, that is if they're not a master of arms who masters every weapon type. But how do you translate this into a game with a single skill encompassing them all? Perks. My guess is among the numerous perks present per skill, some of them being a sort of "sub-skill" while others can be more for general use like fancy moves maybe, maybe with different levels too. You know, it's not because you're good with a knife that you can even use a warhammer competently, neither the later would mean that you can strike a knife surgically where it hurts and with sufficient skill. That's where both perks and attributes come in. There'd be a strength-related perk that lets you be able to lift warhammers, another level of the same perk that lets you strike with sufficient force without draining all your stamina (more related to endurance), etc. There'd be "knife perks" that let you strike faster (speed attribute) or be more swift (agility). But of course these are not solely related to knifes, you can strike a warhammer faster or with more agility, maybe some identical abilities for weapons can be obtained specifically for that type of weapon through levelling the perk for that weapon type. That would mean you can specialize yourself much more into a weapon type and more fluidly. You wouldn't spend attributes points per se, but they could be improved across a great variety of perks depending of what those perks actually requires you to do. Then there's those "fancy moves" perks. Well, to further elaborate on the whole perks thing, I'd say it works as a tree. Say you want to level up your warhammer skills, first you have to unlock the strength perk(s) to be able to lift one (maybe you need to spend 2 or 3 points to actually be able to lift it), then it separates with agility, speed and different moves, each which can be levelled several times, those perks being exclusive to the weapon type. So even as a warhammer wielding dude, you can specialize yourself early on with the weapon, will you only use brute force to smash opponents or will you try to be swift and fast to make your opponent unable to do something?
If you take acrobatics and athletics, maybe there's be swimming and climbing perks. Maybe you can't even swim when starting, that you need to allot a couple of perks points in order to swim, then speed, agility, endurance, maybe a trick or two, same for climbing. But what if you want your character to already know how to swim or use warhammers? You'd be able to attribute a certain number of perks points from the get go.
Skyrim may not work like this at all, but I think it would work great, that you would be able to specialize yourself like never before and that there will be countless of character possibilities... What do you think? Any ideas of how something may work differently or to add anything?
EDIT: I forgot to add something about Hand to Hand. Considering there's only 18 skills, I wouldn't be surprised Block is taken care of in Hand to Hand. Perks would include punches abilities (moves, speed, strength, endurance) and blocking ones (bare hands, weapons, shields and moves maybe). Having a high Hand to Hand skill would make sure you're better to block with anything, put allotting perks points would make you a lot better (and faster) at blocking with a particular tool. Same with every other skill, it's not just about perks. A high Melee skill will make sure you do quite some hitpoints with any melee weapon, but without weapon specific abilities it would be almost useless.