I'm pretty sure I have guessed which skills have been removed (or combined):
MYSTICISM: DELETED.
ENCHANT AND CRAFTING ADDED.
ACROBATICS AND ATHLETICS HAVE BEEN COMBINED (PLACED UNDER STEALTH)
SPEECHCRAFT AND MERCHANTILE COMBINED.
THE MAGIC SKILLS: DESTRUCTION, ALTERATION, ILLUSION, RESTORATION, CONJURATION, ENCHANT.
THE FIGHTING SKILLS: ONE-HANDED, TWO-HANDED, SMITHING, BLOCK, ARMOR (IN TOTAL), HAND-TO-HAND.
THE STEALTH SKILLS: SNEAK, LOCKPICKING, MERCHANTILE/SPEECHCRAFT, ACROBATICS/ATHLETICS, ALCHEMY, MARKSMAN.
This is just a guess...
Do any of you think I'm right...
My guess would be more like;
Destruction
Alteration
Illusion
Restoration
Conjuration
Enchant
Smithing (includes armorer)
Sneak (possibly includes security)
Athletics (includes acrobatics)
Speechcraft (includes mercantile)
Alchemy
Enchanting
Hand-to-hand
One-handed
Two-handed
Marksman
Heavy Armor
Light Armor
I'm not dividing it into groups (magic skills, melee skills, stealth skills) because in Skyrim you could easily be a jack of all trades, you're not confined to picking only a few major skills. So there's no real purpose for dividing them like that o.o
I think it makes sense that they have a heavy armor and light armor. If you're used to running around in light armor and you try to wear heavier armor, you won't be used to the weight and won't be as effective. So combining them is kind of dumb.