Yep, I think divisions for kit are good as well. I raced world champs in Slalom a long time ago, and raced slalom again just a couple of weeks ago, but I no longer want to spend the $$$$ to be competitive for just a few races a year. It shouldn't be too hard to make up some rules to ensure that guys without Formula or modern slalom gear have their own division/s.
Sure, there's hassles creating the extra prizes (I know that very well, I've organised many Wally trophies

) and there's some dilution, but I bet there's a good chance you'd get more than enough extra entries to make it worthwhile.
Looking at boats (because information is available) around the world shows that the idea "we have too many classes" may be wrong; popular, logical, but wrong. The countries that have more classes have more boats, because people can find something they like to sail, and something that fits their budget. So maybe we get too worried about diluting events by having divisions.