[Ultima]

Gguruusa has it. Possible? Yes. Easy? No.

My understanding is you'd need to modify the bootloader to repartition the ROM to have 2 separate CE images. Then you'd need to mod the bootloader so you can choose which one you want on boot. Perhaps one could be default and the second, less used one could be autoloaded when you do a keypress on booting like you do for hard reset or bootloader mode.

Additionally I think provisions would have to be made for flashing so you know which os you are currently flashing.

It sounds like a lot of work to me and would be a something above what the average rom chef is capable. You'd need to crawl on your hands and knees to the likes of cmonex and olipro with some very generous use of their donate buttons to even have a snowballs chance in hell.