Might be a bit late for you, but if you are still looking I've got a neat GUI app project you might be interested in: https://github.com/mfitzp/metapath/
It's scientific software, for the analysis of metabolism-derived datasets. Architecturally it's a simple core multi-threaded application, with additional features provided by plugins than spin jobs onto the queue. There is a UI for workflow construction (like inputs/outputs) and lots of natty visualisations. It's built using Python/PyQt which isn't hugely different to Wx (it was originally written using Wx, but needed Webkit), so could meed your requirements.
Project Github: https://github.com/mfitzp/metapath/
Project homepage: https://getmetapath.org