But I am not sure if anyone wants Text Adventures for Colecovision ?
You've just made Leisure Suit Larry possible, for one thing. And Basic programming, although you probably couldn't save your programs unless you used an advanced PCB like my Activision PCB, which can store up to 256K of data on an EEPROM (that's what Boxxle will use) but is limited to programs of 64K or less.
Also, if the keyboard interface were to contain 24K of RAM, then you wouldn't need to plug in the SGM at all. In fact, if it's done right, the Adam Super Game conversions I have released (Dragon's Lair, Zaxxon Super Game, Buck Rogers Super Game and SubRoc Super Game) would work without the SGM plugged into the CV console. As the SGM is compatible with the ADAM, we know it's possible to avoid RAM addressing conflicts.
EDIT: Perhaps Daniel Bienvenu would be interested in finishing his "Château du Dragon" with this keyboard interface. Also, it would be interesting to see if the Zork ADAM games could be ported to cartridge.