This is my dream. However I think my target market is smaller and less willing to pay (personal rather than business). However maintenance is low effort and I want the product for myself. So even if it doesn't make much or anything I think I will be happy to run it forever.
The ultimate dream would be to make enough to be able to employ someone else part time, so that there could be business continuity if I wasn't able to run it anymore.
Instead of system wide PTT per-app you may consider some software that mutes your mic for all apps as PTT, then just leave the mic "active" per-app.
I don't know if a tool that will do this but on my mouse I have configured a mic mute toggle. So I push to start and stop. However technically I don't think there is any restriction to setting up PTT via this mechanism.