Discussion of development of software for any "obsolete" computer or video game system.
By the way, previous discussions wondering about double-ended NES/Famicom carts happened in threads below. Both times user Fisher mentioned a brand called Hydron that actually made carts like this. The 2019 post has a link to a blog post (in Portuguese). The 2018 post includes an attached picture (uploaded/hosted on the forum) of an open cartridge showing what the board looks like.
It's the case that'd be expensive in that case. Molds are >10k. Then you have to consider how users will take it, collectors will balk at something that looks like obvious, visible cost cutting.