I gave up on guns with changing functions like multiple barrels, frames ect. It seems I would find the best combination and the rest would just lay around.
Now if I want a different configuration I just buy the gun the that fits the need.
Multiple functions are a better idea if one lives in a area that restricts the ownership of how many guns one can have.
Extra accessories when one goes to sell them normally bring a far lower price then one paid for them.
Buy more guns then you have available the one you want when you need it.