Not in the middle of execution; there are various ways to handle pre-script setup, but once the script starts running, only boolean values can easily be captured.
Though, it does give me a curious thought; if you execute the script as a relay script (either info or override should work), you could have it stop, then at the end query the user for info, and have them submit the relay page with such info and then the script could "resume" (actually it would be starting over, but you could script ways to make that a semantic difference only). But I don't think there's much you can do on the gCLI.
Edit to add some background:
This conversation actually came up before, as to requesting additional user_X() functions, and indeed I once pushed for it. The basics are that even user_confirm() can be easily abused, and cause aggravation to the user, as having to provide ongoing input kinda defeats the purpose of running scripts. The existence of user_confirm() was considered a bit of a "necessary evil" just in case a script might do something unexpected that could cause real problems. When I last pestered the devs about additional user-input, we were given htmlform (and there was much rejoicing).
