Well, the thing is that all of the improv host clubs I've seen have been sloppy D: I figure a little improv is okay..but that would have to be between the lines of the script. We want to look professional right? Would it look great if all of were standing around stuck on what to say? I think we can have fun with the script, since we're all contributing...but I paid to go to a host club, and the firt half of it was just them running around and talking to eachother about what the hell to do.
This is a 'performance' kind of panel anyway. It's supposed to be 'teaching' people how to be a host instead of just doing an actual host club panel, so I think at least moderate to maximum scripting is neccessary to get things to move along smoothly. You might not have to say the lines word for word..but something along the general lines would be great.
It might be an added effort to write and learn a script, but the performance would be much better for it.