I think this argument is flawed for a few reasons. First of all, you really can be competitive without full team doubles. On the Worlds score sheet, tumbling only counts for FIVE percent of the entire score. Having a few doubles on your team alone won't win Worlds, that's for sure.
Second of all, doubles are hard, and that's why there aren't so many of them. Imagine if you had a division where you HAD to have doubles, not just fulls. I can't even imagine there would be more than a handful of teams nationwide that would even qualify for that division. And really, how many teams have full team standing fulls/doubles? I honestly can't even think of one. If we're basing divisions off of a hypothetical situation that hasn't even happened yet, then there's something terribly wrong.
Lastly, you seem to be making an argument for gyms with new level 5 programs. No matter what level, you can't expect new small gyms to come out of the gate winning every competition. Older teams have been raising athletes and training them for much longer, so obviously they're going to be more experienced.
The biggest thing is that I can't help but feel that your post promotes like...and equal chance at winning, not an equal chance at competing. A team that just graduated from level 4 to level 5 really shouldn't be able to suddenly appear and start winning Worlds. There should be a natural progression. What you seem to want is that dreaded "50 National Champions" at one event. The nature of competition is that some teams will vastly out skill the others, and that's what working hard and training is all about.
To sum it all up - a team with fulls certaintly can compete against a team with doubles - there's a lot more to a routine than just tumbling. But if you want one of the top spots at Worlds, start working harder, not clamoring for a new "restricted" division.