Is it worth it to switch??

[Stewart_Reptiles]

I need to know if this is enough room for a small rat colony.

Yes you could build something like this which would take very little space

What order should I take to see if they'll switch to FT rats? Should I get them on rats first then FT or FT then rats??

I would recommend switching to rat first unless they are already used to F/T, once they eat rats with consistency (6 to 8 consecutive successful feeding) I would attempt switching to F/T

If switching doesn't work for the two BPs, and they refuse to have anything to do with rats, would it still be worth it to breed rats for the other two BPs and the corns?

Absolutely!

And this is the breeding schedule I used to use when housing 2 females per tubs (if that helps)