My idea has nothing to do with cosmetics... more with typing feeling and sound :
Just got a brand new compaq 11800 with nice MX brown, but keycaps look very cheap compare to what you can see on old keyboards. It's made of light plastic with no reinforcements, just a thin cross under top of key, so my idea is to make them heavier and more solid by filling them with resin (epoxy for example) up to cross stripes top (if you fill more the cap will be unusable).
Pretty sure this would enhance typing feeling and typing sound as some keyboards are noisy not because of clicking switches but because of this kind of light-built keycaps hitting the switch case.