Board Thread:General Nerf discussion/@comment-26431461-20190613203258/@comment-2234967-20190613204159

K'Nex sort of did that with their K-Force blasters. You could also assemble them into alternate modes, or straight up make your own.

Kit blasters would be neat but man, I don't think an eight year old could do a whole lot of wiring and easy-to-lose spring placement. I can see a third party doing this, kind of like how there's DIY Raspberry Pi mobile game devices you can order online and build at home.