Sorry, my bad, I misinterpreted your OP. I was thinking you wanted to restrict magic using characters to 1D3 MP per day, not recovering 1D3 MP. That's a totally different kettle of fish and if that's how you want to manage magic in your game it's not a bad way of doing it.
Personally, I'm not a massive fan of any form of magic. In my experience with D&D & Legend creative magic using PC's can often reduce an encounter, especially if they have the luxury of being be able to prepare ahead of time, from being challenging/difficult to ridiculously easy. I was running the Caravan adventure from RQ6 Book of Quests. The party had 2 sorcerers with different grimoires. In the semi-climatic battle against far superior numbers the PC's won easliy, here's how: Both sorcerers had grimoire skills higher than 70%, by casting Attract (Missiles) on a huge shield and a combination of Damage Enhancement and Damage Resistance across the party it meant that the opponents on a successful hit (hard enough already given the PC's combat styles being a good 20% higher) could barely damage them unless they rolled max damage for their weapon or managed to generate 2 CM's via a crit, conversely the PC's were basically doing a minimum of 8 damage - generally sufficient to incapacitate a foe with average HP, particularly if a CM was involved in one hit.
So, I don't like magic full stop. But it's fantasy gaming and magic is an expected/inherent trope that we as GM's just have to manage as best we can.