I'm not sure it would be all that useful, considering the amount of variables involved in something so seemingly simple as making kits. You'll have people who have no idea what they're doing, screwing things up, going off on a rant and rating a really nice premium kit quite low. And on the opposite end, you'll have experienced winemakers adding a whole slew of tweaks to a cheap kit and giving a high rating to a kit that might otherwise be barely drinkable. Then you have people that follow the directions to a tee, some that deviate slightly and some that deviate drastically, some that bottle age, some that bulk age, some barrel age, some don't age at all. Which brings us to the biggest factor. How long has it been aged overall? How would any of that get reflected in a numerical rating system?
As if there weren't enough problems presented above. Consider that the quality of the juice in any particular kit absolutely has to change year to year. By the time someone is either ranting or raving about a particular kit, if you're able to find the same kit at your LHBS, the juice is in that kit is likely to be from a harvest at least two years after the kit being reviewed and possibly even sourced from a different vineyard.