I posted this on reddit last night but thought many here might not have seen this thing yet, so check it out.
Playing Sega Megadrive Sonic on a Sega dreamcast VMU inside a Sega dreamcast joypad. This is the Sega'est thing ever. I need this. Put me on top of the want-to-buy list. This is just so incredible. Oh and I'd like an HDMI out coming from that joypad. I'm kidding. No, I'm not.
My dream for this, is to be able to natively interface with the Dreamcast. So maybe have a switch on the side, where it is a mode to fully emulate a VMU, I know there is already a good emulator out there for it. Make this have the ability to fully save and everything a normal VMU does, I would pay somebody good money if they could do all of that if I was made of money haha.
I'm working on my own version and what you want is pretty much not going to happen with the limited space inside of it. Even if there is an emulator of the VMU I'm sure it's just to play the games and not emulate it's functions.