The SL-15 uses a p-mount cartridge, of which your choices are severely limited to conical and bonded elliptical moving magnet designs.
Not at all. Simply find an amazing P-Mount cartridges designed by Stanton back in the 70s/80s with Nude Stereohedron styli on them, they are high compliance.
What’s wrong with MM design?
Stanton made low impedance and low output LZS version of their top on the line MM too, those carts are Moving Magnet but works with MC phono stage or headamp.