you could have one title and description per current category and then consolidate all categories into one and delete the empty ones. This way it should work from what I understand unless you have loads of completely different keywords in each category.
I had the same issue when my campaign was migrated.
I did re-structure my account into about 20 campaigns of like ad groups.
DO NOT DELETE your unused campaigns... you are grandfathered in and wil never get more than 20 back. I just renamed mine to unused 1, unused 2, etc. and paused them. That way later on I have plenty of available campaigns available to use. :)
download your account into excel and reorganize your campaigns. PM me if you need more details.