This was a request on reddit. I couldn't find anything matching the description, so I made it.
This mod stops Magicka regeneration. You'll have to rest, wait or use potions/absorb to regain Magicka, like in Morrowind.
(Atronachs still don't get Magicka by resting or sleeping.)
If you only want to restore Magicka while really sleeping in a bed, check the ini file for settings.
Other than in Morrowind it is not possible to "sleep" in the Wilderness without a bed, though. I'd suggest a mod like Maskar's Camping.
NEW in 2.0: Full Morrowind Mode!
Turn on this mode in the ini to make Magicka regeneration based purely on Willpower (optional: Intelligence), not on your max. Magicka pool - in vanilla, your Willpower determines how long it takes for your whole pool to regenerate, no matter if its 50 or 500.
You can also use the Willpower-based regeneration during gameplay, not only on sleep/wait. Check the ini file.
If you want to fully heal on wait, but still use Willpower based regeneration during gameplay, you can play around with the values a bit. Setting the multiplier for Willpower super high and the GameModeMult very low (roughly multiplying ReturnWil * 100 and dividing GameModeMult / 100) will achieve that result.
set lMLMReturnWil to 15
set lMLMGameModeMult to 0.05