Lol, gohm, you've got a lot of ideas there! Good one. Looks like you are warming up to the idea of instant messaging eh?
However, from the perspective of the interviewee, Id rather have ample time responding to questions
Don't really want to pressure the guy with impromptu questions, might risk them to misintepret questions, misphrase his answers or spill out unnecessary stuff. Perhaps he can't recall quickly some things (like technical details) and needs to pull out a file, etc etc.
It'll be different than discussing ideas, cause everyone will know in advanced what the topic is, and have their own thoughts ready at hand.