Hello all,
Recently I have been on a Morrowind playthrough. I installed MSGO mod and delayed tribunal start mod. One thing that really bothers me is the magic system. Is there any mod out there that improves the magic system and will not conflict with MSGO? I would prefer one that decreases spell cost as you skill increases.

Pandy's Regen is a good option. Since the demise of Planet Elder Scolls, it no longer has an official home, but the file is still available from Morrowind Modding History. And Pandy's Cheats is great for screwing around.

My personal choice (if I use mana regeneration at all) is "Fair Mana Regen" from GlassBoy, available on TESNexus.
Note that there is another one, called "Fair Mana Regen v2B" from Smoke, also available on TESNexus. The second one is based on the first one. I prefer the first one because it lets me change the regeneration rate - the second one is probably more sophisitcated.

"Fair Mana Regen":
"This Mod ... calculates your maximum magicka to determine what 1% of your magicka is, and willpower is used as a fraction of that 1% to determine how much magicka you regenerate per second, so at 100 willpower, no matter what, you will regen your magicka completely by 100 secs, if 50 willpower, you will regen in 200 secs, and so on.
Updated:
Now this package includes two more mod files, in case the initial magicka regen was too fast for your preference,
>Fair magicka regen (One percent) regens your mana completely from zero in 200 secs [at 50 willpower]
>Fair magicka regen (Half percent) regens your mana completely from zero in 400 secs [at 50 willpower]
>Fair magicka regen (Fourth percent) regens your mana completely from zero in 800 secs [at 50 willpower]
>Fair magicka regen (Tenth percent) regens your mana completely from zero in 2000 secs [at 50 willpower]
FYI: one morrowind hour is 120 seconds, one morrowind day is 2880 seconds (48 minutes)."

"Fair Mana Regen v2B":
"This Mod calculates your maximum magicka to determine what 1% of your magicka is, and willpower is used as a fraction of that 1% to determine how much magicka you regenerate per second.
This Version will now work with any addon race, birth sign, or mod that changes your magicka multiplier. It checks your base magicka against actual magicka to give you accurate regen rates, will also work with magicka fortifying enchantments, spells, and potions.
It works properly with the Atronach birthsign. (Disallowing regeneration.)"

In both mods mana regeneration is useless during a fight as it simply takes too long (contrary to mana regeneration in Oblivion where mana can regenerate completely during a fight, if you manage to survive without using mana for some time, by keeping your distance from attackers, for example).

From the description it sounds like Pandy's Regen, mentioned in the post before this one, is also delaying mana regeneration, but achieves it in a different way.