Aren't there other ways of balancing things than just remove stuff? The Alteration method could be limited to a rather distant perk with a skill req or something.
Problem is that gimping Unlock to a degree where the Lockpicking skill is not useless, would make the Unlock spell useless. Consider the simple scenario where Meya the Mage comes to a locked chest and cannot open it with her spell. Meya will have to either pass it by or pull out a lockpick. I'm pretty sure most players would pull out that lockpick. And if that is the end result anyway, why not just start there?
But while it may be more 'realistic', at the very same time there is no option for a Mage or a Warrior to open chests. I can understand not including bashing the lock, [its very stupid not too and would be very easy to implement compared to other things], but completely removing a spell that many wanted for balancing purposes isn't right. As of right now locking picking isn't balanced and the perks are completely useless. I thinl that they should of balanced the perks more and kept the spell in. It's just Bethesda being lazy.
I think lockpicking is not balanced due to one simple reason: If a player reaches a lock that he or she cannot open, most will be annoyed, and they definitely will not return when they get good enough, because the loot is seldom worth it. Perks are not balanced because the only real mechanic they have to work with is the annoyance of the mini game. Had lockpicking been a real-time roll taking e.g. 1½ second per attempt, with the perk giving autosuccess and only taking ½ second, most thieves would find the perks pretty useful.
Overall I don't think theres a big reason we don't have lockpicking via magic with costs of say 100, 300, 600, 900, 1200 mana for novice, apprentice, adept, expert, and master locks. I think those costs would make it fairly prohibitive if you didn't do significant investment in alteration.
As long as you are not in combat, magicka regen is not really a problem. If you have enough magicka to cast the spell, you can do it.
Edit: Fixed a few spelling goofs.