Would I be able to alter sensitivity in this way?

Planars are somewhat foreign magic to me, I understand that for the same cone on a dynamic driver you could increase windings on the motor or use a bigger magnet to get different amounts of power out of the same cone provided that the cone maintains its stiffness and other materials could handle changes to excursion, but just increasing magnet strength on a planar? Like whaaaa?

What I'm thinking is R&D 3D print some templates to allow sliding the strips into place over the existing magnets. The "have fun and find out what happens" has to be worthwhile though and would need some kind of tangible, non-catastrophic result.

I do this kind of thing a lot. I converted a 1995 Honda CR-V to E-85 just because I could, once, and I learned a ton while doing so. I then also experimented with custom fuel blends. Even mediocre results are worthwhile, educationally.