What about Athletics and Unarmored?
I personally think that all those should return, and the best way to do that is to merge them into one skill - Unarmored (each level in this skill will increase armor rating by 1 if wearing no armor at all: head, chest, hands, feet):
Spoiler Stoneskin - Req: 0/20/40/60/80 Unarmored; Effect: Adds 20/40/60/80/100 armor rating if wearing no armor at all: head, chest, hands, feet.
Speed (gonna need a better name for this one) - Req: 30 Unarmroed & Stoneskin; Effect: Increases attack and cast speed by 20% if wearing no armor at all: head, chest, hands, feet.
Swiftness - Req: 60 Unarmroed & Speed; Effect: Allows to preform a doge roll if wearing no armor at all: head, chest, hands, feet (still need to think of a proper command for doing it).
Athletics - Req: 50 Unarmored & Stoneskin; Effect: Increases walk, run and sprint speed by 50% if wearing no armor at all: head, chest, hands, feet.
Vitality - Req: 90 Unarmored & Athletics; Effect: Increases health and stamina regeneration by 50% (this perk is NOT disabled by armor).
Acrobatics - Req: 50 Unarmored & Stoneskin; Effect: Increases jumping by 100% (this automatically increases height needed to take damage from falling by 100%) if wearing no armor at all: head, chest, hands, feet.
Arial Attacker - Req: 70 & Acrobatics; Effect: Allows mid-air attacks if wearing no armor at all: head, chest, hands, feet.
Supreme Footwork - Req: 100 Unarmored & Swiftness/Athletics/Acrobatics; Effect: Allows movement while preforming power attacks and all other attacks which disable movement if wearing no armor at all: head, chest, hands, feet.
Also...
Jump while running anyone?
Aren't we already able to do that?
How about enhanced movement speed while blocking?
Isn't there already perk for this in Block?
Faster movement speed when over encumbered?
No... just no.
We are lucky that we can move at all.
No need to increase that speed since having too much stuff will start to lose it's meaning.
I think we can do that also.
Faster movement speed when Health is below a certain point?
This kinda makes no sense, really.
Edit:It would also be sweet if there was a Feather spell for Alteration in Skyrim, but that it has a function of Slowfall and Jump spells from previous games (would allow you to jump higher, greatly reduce fall damage and slow down your jump/fall speed a bit - kinda give feel of being in low gravity zone).