If this does end up working as intended, I have no plan to sell this. But rather I'd make it open source so that anyone can build it from like $25 of parts. And it saves me from Nintendo coming after me.
Recently I saw a video about a GBA SP cartridge swapper thing where you could insert 3 cartridges at the same time and use a little switch to swap between them. My initial response was why doesn't something like this exist for the switch so that docked mode players can just swap between games...