I got around this MT limitation for Dama by making her a Merinita with a high Faerie Magic score. A magus who knows Faerie Magic can use twice their MT and twice their FM scores in a season, as long as half of the vis is Faerie vis. Now you can hit 40 pawns of vis with only a 10 in MT and a 10 in FM, as long as 20 pawns are Faerie Vis. That's only 550 experience points, versus the 1050 needed for MT of 20. A score of 10 for both of those skills seemed far more reasonable than trying to go the full MT. Cooperation can help increase the lab total, but then you have to overcome the social aspect of working for another magus. In a troupe, you can handwave this, but for NPCs, you can't.
Additionally, in the case of Dama, she has seasons spent creating her legacy, training an apprentice, establishing her covenant, all of which consume her time and divert her from personal improvement.