Athletics I would be GLAD to see gone, since you want to run to move faster but to run levels Athletics, it was annoying in oblivion seeing what that did too speed. Now if all skills will level you in skyrim, I can see potential issues if you go and get yourself too many semi-combat or non-combat skills rather then focusing on more dedicated combat skills early on. This would also mean the same to mercentile, more so when considered already what would happen if you levelled mercentile and speechcraft too early in Oblivion after all... you'd end out with lots of personality that monsters would happily digest as they eat your personality over-filled backside.
The Seperation of one and two handed weapons I am not sure about, since both swords and axes easily go into both categories, what would that do to weapon perks? While I am hoping for more weapon variety over what Oblivion had, I am sure there are better ways to seperate it out then one and two handed weapons, after all I am sure a claymore has more in common with a long sword then a halberd. Then again, it really is not biggy if it is seperated out like that, it still works fine, just against my personal preference really.
We have sprint now,so athletics may have gone,or will be athletics and acrobatics combined. If you jump when sprinting you'll leap/jump further,because of momentum.Obviously not as far as jogging or walking when jumping.
Mercantile was useless..why? Well you could argue spellmaking made a few skill useless for a start because of expliots. But anyway...When bartering etc,your using your speechcraft,your charming,liked,smooth talking...all this = speechcraft and speechcraft only,no need for mercantile,because it's the same thing.
You say your not sure about one handed and two handed. Well...to me it makes sense,and if i was a developer i would do the same. Now where you say a claymore as more in common with a sword..well...your right,thats why perks and ranks allow you to specialize in swords etc. Say your good at the two handed weapons skill....that means as two handed goes up you will be good at two handed swords,axes,hammers,halberds etc...Then from there you specialize in swords say. Now you are better with two-handed swords,than you are with two-handed axes,but because your two-handed skill is going up,you can still use two-handed axes,hammers etc well,because your good at two-handed. But because you went down the sword/blade route,your even better with two-handed swords....because it's your speciallity. It makes complete sense to me. So say your claymore ( swords your speciality ) gets knocked from your hands or breaks,you can now use another two-handed weapon well,because your good at two-handed-just not as good as you would be with a two-handed sword.....hope that makes sense. Again this is something i would do as a developer too,it makes complete sense.
Some people are not understanding what bethesda are trying to do here. They are seeing 27 skills,then 21,then 18,and seeing as rubbish. That is not the case. It needed looking at in my opinion. What they are really doing is giving you the same or if not more skills. With ranks and perks the options are way better. Mercantile needed to be merged with speech,it's the same...so get rid of the name mercantile. Mysticism ( as a name ) is not there,but the skill/spells in or under that name are,just moved around into different spells skills...again that makes sense.
The 18 skills + the ranks and perks will end up being more and better than the 27 skills from daggerfall...don't just look at the number 18,that to me it's an illusion ( if that makes sense ).
All this needed to be done in my opinion,it will work out alot better and be more in depth,and will allow you to specialize more in the long run.