um...yeah k sure.
Greg, why should armor stop Magicka Regeneration? magick Casting sure but Regeneration?
No, heavy armor shouldn't impact casting at all, because lore-wise it's not tied to your range of motion whatsoever. The closest explanation we get to how magic actually works is in some volume of 2920, though I can't recall which, in which Sotha Sil explains briefly that belief is the primary factor of spellcasting. The students are being subjected to a test of their ability to resist fire, and they succeed because they "know" the fire will not hurt them.
Magicka itself flows down from Aetherius through the sun and stars, suggesting that it's basically everywhere and living things naturally absorb it. Some have deeper reserves than others, and some are able to more quickly absorb it, and some aren't able to absorb it from their environment at all, and must absorb it by absorbing the magicka of others. It would make sense for heavy armor to cut people off from ambient magicka to a degree. I think it works better for gameplay anyway. In the old games when you got your skill high enough any drawbacks from heavy armor were eliminated to the point that they might as well not have existed. This way there's a consistent penalty for wearing heavy armor that gives the play style an inherent disadvantage.