Second, I never leave the catch container in the vac without running the vac to keep the air flow moving.
This can be quite impractical at times, especially when doing large cut outs. I'm not saying you can't, but I can say I have sold more bee vacs to people that had overheating issue with bucket vacs than any other design.
Not really sure what you find impractical about it? When the catch bucket is in place, I leave the vac running to avoid overheating the bees. If I want to stop the vac for any length of time, I simply remove the catch bucket from the bucket vac to allow the bees more air. When I'm ready to vac again, I simply brush any stragglers of the outside of the catch bucket and insert it back in the bucket vac and resume vacuuming. It literally takes about 10 seconds.
However, as I've said before when discussing the different types of bee vacs...They all have their advantages and disadvantages. :)
While I think your vac is a great design and have heard nothing but great things about it. Personally, for me, a bucket vac in many cases, simply makes more sense. For example, when a local Chemical Plant calls for me to remove a swarm, in many cases, they won't allow you to bring a vehicle into their facility. I've had to walk a couple 100 yards and climb up a couple levels of scaffolding to reach swarms at these facilities...Something pretty easily accomplished with a bucket vac slung over my shoulder, but something that would be quite impractical with your style of vac.
As for all the people that you know that have had overheating issues with bucket vacs...I really can't speak for them, I can just tell you it hasn't been an issue for me.
Honestly, as much as I've read about dead loss with bee vacs in general, I was absolutely shocked after the first several times I used my vac and observed absolutely none. My best guess is that most people have their suction set way too strong.