Currently on live you can't take any enhancement that buffs an ability you don't possess. This is right and proper, IMO. In the new enhancement trees, however, it seems like buffing an ability you don't have is the norm. Been working on a respec of my pally today, and just that alone shows:
KotC tier 1: (Available at level 1)
Extra Turn Undead (pallies can't turn undead until level 4)
Divine Light (buffs turn undead; again, turns are ML4)
Extra Remove Disease (pallies don't get remove disease until level 6)
KotC tier 2: (Available at level 2)
Improved Turning (again, level 4)
Divine Might (requires turn undead, level 4)
KotC tier 3: (Available at level 3)
Improved Restoration (buffs Remove Disease, which again is level 6)
Sacred Defender tier 1: (Available at level 1)
Extra Lay On Hands (pallies don't get LoH until level 2)
Improved Sacred Defense (Sacred Defense is a stance acquired from tier 3 core ability, minimum level 6)
Sacred Defender tier 2: (Available at level 2)
Improved Sacred Defense (buffs the stance you don't get until 6)
Sacred Defender tier 3: (Available at level 3)
Improved Sacred Defense (still buffing the ML6 stance)
Greater Sacred Defense (same deal, now with more "no effect")
Sacred Defender tier 4: (Available at level 4)
Greater Sacred Defense (Just how much can we buff a stance we don't qualify for?)
Swift Defense (Apparently a lot! Still buffing that ML6 stance...)
This is just what I ran across while designing a single build. No doubt this type of thing is all over the other trees. Don't you think this will be very confusing and un-intuitive for new players?