I'm still experimenting,,but have tried putting banner (edited) ads in notices. It seems to work well, users can dismiss the ads which I like. The banners are nicely responsive.
Nope! I don't see any reason why this would be a bad idea. In fact it's probably a good one! All the notices are doing are wrapping what ever you put into the 'message' box in <div> tags and giving them a little CSS, nothing special (or harmful).