With perks one armor skill makes sense. Just like how one handed weapons makes sense. Heck, this way we may even get no armor, light, medium, and heavy again via perks with one armor skill.
When i did my 18 skills a while back i had heavy and light armour. But i believe i'm wrong now. With perks like you say,armour will probably be a skill on it's own,does make sense.
I also said that security and sneak would be combined too,but now if heavy armour is not there,maybe security is separate after all. I thought/still think it makes sense,for sneak and security to be combined,but if thats the case and armour is a skill that would leave an empty slot in stealth. Mercantile as been combined with speechcraft,of that i have no doubt,they are one and the same.
You use speech,smooth talking when bartering etc,so that comes under speech,mercantile will not be it's own skill now. Security must still be a skill on it's own,if there is no light armour.
But i didn't think security would have enough decent perks to be separate,but it must do really,because if they are combined as well as what i've said above,that would leave another skill to find...and i can't think of one. So i guess for now sneak and security are separate.
COMBAT: One-handed, two-handed, armour,hand to hand,block,smithing.
MAGIC: Destruction,illusion,alteration,restoration,enchanting,conjuration.
STEALTH: Archery,Alchemy,Speechcraft,Acrobatics,Security,Sneak.