Will this in any way weaken the frame?

for all technical aspects: Yes

altering the plastic via heat or grinding it down will weaken the overall strength of the frame/material

h/w, i have not heard of any problems w/ people soldering or dremeling down the plastic, as long as they kept it moderate/low....

I dont recommend stippling... there are better alternative for better gripping surface.  Agrip is the best imho, but grip sleves, and skate tape are also worthy alternatives.  If you stipple you'll regret it if you ever have to send the gun back for service, need to carry concealed, or if you go to a training class that's more than a day long.  And besides.....you really dont need THAT much surface friction to control the gun...at least you dont if you're using proper technique.   I shoot a G29, occasionally with hot loads.  I've got agrip on it....NO pinkey rest base plates, and it has more than enough gripability.....rainy, sweaty, cold, hot, it doesnt matter.   Did a class under the hot nevada sun...4 days, 800 full power 10mm carry rounds, countless dry fire drills, gun never slipped and my hands werent chewed up.