Ok, I guess you're right about that stuff (until thunderbird sync is released), but I'm not convinced using gmails web client is the answer. I think most email web clients will give you this solution, no? And if not, then there's nothing to complain about because you've selected your tradeoffs.
Discussion
I tried a lot a few years ago. Gmail was the best fit for my needs. Gmail originated as a side project from a google dev. He invented it because he himself needed the features because no other app provided them. Maybe there are better solutions these days?