Lots of these comments are really confusing cause I dumbing biggy. So I explain aswell with my words:
You can already get an enchantment that increases mana gain, it's called trench.
You need level 70 mining to be able to use trench. And you can buy it for 800k mana if you have level 75 mining AND Hephaestus rebirth.
Trench gives you 3x mana and 3x mining experience for every block broken with a trench pick (not including the extra blocks in the 3x3 area).
I think that adding another enchant that increases mana would be a bad idea because there is supposed to be a challenge to earn your mana. I believe that prisons are supposed to be a grind and make it challenging to get mana/money.
But if you have some kind of excellent idea that I didn't understand, then please make a suggestion on the suggestion page
https://suggestions.manacube.com/
I am all for adding new stuff to Olympus.