I was wondering it as an experiment to have a WPS class that has Qt elements on it, instead of PM.
No experiments needed, the results are already known: if the thing is well-crafted, it will look nice. But at what cost?
Here are the DLLs that will drawn into the WPS if this widget or whatever links to nothing but 'qt5core.dll':
libcn0 stdcpp6 gcc1 libcx0 libc066 z1 icuuc icuin icudt pcre260
Each one of these links to other stuff - and more than likely, this thing will link in still more stuff - none of which exists in the WPS process currently. Do you really want to burden your entire system from the time it boots up with the shared memory demands of some marginal new widget? I hope not.
And why? What is in such desperate need of whatever Qt has to offer? If you were proposing replacing the Desktop with Qt, I'd be a lot more sympathetic than I am to the idea of tacking on some Qt-whatever "just because you can".