Yes, you could.  No one sane would make it though -- it would have a *very* limited market and the prototyping costs/development would be hell.

very far but cheap no

I wouldn't want to sell it...
I just thought it would be a really fun project. How could I do it? How could I connect the processors to the screen and keyboard and stuff? Could it have a TI Basic interpreter? To what extent could I pursue this?

You could do it by buying the nessicary parts and clicking/soldering them together.  And you could make a BASIC parser.  Why all the work though?  It will cost you *a lot* and will be more work than necessarily needed.

It would be cheaper to wait for chronomex to finish z680k, his z80 emulator that runs on the 68k calcs.

I suppose it wouldn't be impossible, but I don't know that I'd consider it a "fun" project. It would definitely be simpler (and quicker) to just buy an 89 (or a V200, but sadly they are more expensive).

Would you want to have some sort of a game-pad in stead of the whole keyboard then? Either way, you'd better start with an 89 or 200 as base and just emulate 84 and 83 on'm.

If you want to make an actual "pure gaming" device, however, with and actual gamepad and all, you'd have to make sure that you can find enough games or edit games to work with only a d-pad, and a few additional buttons. That's the sad thing about TI-games, most games have somewhat similar controls (arrows + 2nd and Alpha), but not all of them do.

I have been thinking of such thing as well, basically a calc with just the buttons that are actually needed for games. For a case you could look into 3D printing services, furthermore I couldn't help with this.

Is there an android port of wabbitemu?

There is!

Edit: I could as well just contribute to this discussion. It's cheaper to make a calculator in an FPGA.