Aesthetically, I won't argue, some armor looks very cool, but a couple of things on your other comments.
Remember, that the pen you take from armor isn't just a Sap Pen, it's a pen on all of your pools, so it doens't matter if it doens't cost Sap, its still going to jack your health bar, which, as a mage, is likely MUCH smaller than your sap bar. If you have a spell with no Sap, and no health Credit, then you have to SERIOUS range and time credits, making you uterly useless for doing any casting anyway.
Using lower level spells that you can cast often isn't the solution either; try casting Cold 2 on Hard Kipee and see how long that takes, especially with the Time and Range credits youd need to make it not cost any sap or health.
As fas as enchantments, as far as I know, the pen still hurts them as well, they just have a cast time of 1 sec and never fails, but who cares, casting with that armor on will drain the enchantment so fast it won't be worth it and if you have to rapidly adapt to the combat situation you are in trouble. Sometimes you need to drop that Acid spell and cast Fear because your tank accidently agro'd 2 or 3 monsters. If that monster charges you and all you can do is cast acid at it, your likely toast, heavy armor or not.
Sure you
could have a mage in heavy armor sitting in the back using enchantment, but
why? Especially when with a good wand and properly edited spells you can deal out tons of damage, quite fast, and repeatedlywhile at the same time having the ability to adapt to changing combat situations. Its a bit like telling a motocycle racer to wear a bunch of heavy armor plating while he rides to protect him if he falls... he could, but why? The armor would almost certianly ensure that he falls, and if he falls the race is already over anyway...
Your misconception here is that as a caster you need to stay alive longer. Thagt's for tanks,whose job it is to stall. Really, as a caster, it's not about staying alive longer, its about killing the other guy as quickly as possible and not letting him attack you.
Sides, it shows incredible grit to go into combat essentially naked