default is fov_desired 75 and viewmodel_fov 54. the max fov_desired is 90, so the max viewmodel_fov should be 64.8; 70 (not 90+) is a round number, reasonably close to 64.8, was already the max slider value, and looks decent/has few graphical glitches, so 70 should probably be the max.
min viewmodels look pretty bad for some weapons, but worse yet, they don't accurately depict where projectiles come from (same with adjustable viewmodels).
we've been blessed, maybe spoiled, to have the astounding customization options we've had (huds, viewmodels, graphics configs), but these are not the features that will attract players and viewers. things like skins, standardizations and a level of polish are all necessary for the competitive scene to grow, but that entails some sacrifices.