The best UI framework to get stuff done is still Qt after all these years. There may be something that lets you do simple stuff easier, but nothing comes close to the power of this fully armed UI toolkit. Coupled with Python it becomes a lot of fun too.
That said, a five-six year old app that's only been quickly added to and never rewritten nor cleaned up does get a bit ugly. Maybe time to take a few days at some point and fix it up and make the networking side better.