We work on Mumble in our spare time and as such developer time is scarce. We try to focus on what we think most users are going to benefit from. There's a long "Would be neat to have X" list ;)
One goal for the future is to make Mumble more modular which should make creating such a specialized client feasible without much extra work.
If someone here is interested in C++ with Qt and wants to contribute to a FOSS project used by nearly 400,000 users monthly we can always use more hands.