I've never seen the effort involved in making a nice quick-feedback REPL-style affair pay off. Perhaps for certain types of game it would be worth it, and perhaps amortized over a long enough period the result would become value for money. My experience has been that making a script system work that way, and work reliably, and provide a nice interface, just takes up more time than you end up saving.
Anyway, all the programmers I've known would want good debugging facilities as well, like the ones you get in Visual Studio/ProDG/Code Warrior/Xcode/gdb/etc. - oops, only kidding about gdb! This thing really needs a GUI. This all just expands the time-suck further.
That's not to say it can't be made to work, of course! People can do anything, if they set their mind to it hard enough, and if they wait for long enough, maybe it will even become value for money.