What I _would_ like to see from the original manufacturers is an actual "mini" system, reimplemented using modern hardware components, and using software improvements (filters, upscaling, etc.). I would even settle for an FPGA implementation, which companies like Analogue are currently cashing on. The original manufacturers have an obvious advantage they can use, but it takes more effort than slapping together an emulator and some ROMs.
It would also be great to have an official digital storefront specific to these systems, with the entire game library, or as much as they have the right to publish. Similar to what Nintendo has done with their legacy systems, just separate from the Switch itself. It just seems like a huge wasted market opportunity to not do this right.