It isn't the mechanical specifics of the weapon, the whole approach is flawed. The critical component is the nut behind the trigger
Here's a guy with a revolver that holds six:
There are people nearly as fast with civil-war era revolvers and bolt-action rifles, or even the bow and arrows.
A fixed magazine that holds ten is what the SKS is, until somebody modifies it.
Yes they are simple mechanical devices, and it would be even simpler to bypass whatever damage your solution did to the weapon.
A weapons ammunition capacity is almost completely meaningless if nobody is shooting back.
The reason we can't get any common sense public safety legislation passed is because we've been stuck on this stupid attempt to ban features for 30 years, and it hasn't done the slightest bit of good anywhere, no matter how many of our historic firearms idiots destroy, how much legal jeopardy you put law-abiding people in, or how much unnecessary expense you add by passing laws about stuff you don't even understand. (How Feinstein has managed to be the leading voice for this legislation for this long and still not know the first thing about the subject is mind-boggling)
20 years later I still get pissed thinking about those million Garands getting burned...that kind of idiocy is why there's no productive dialogue on this subject.