Maybe piggybacking on existing platforms is a way to go. You already have an API, maybe tying in a few major orchestration platforms like Zapier, n8n, make.com, and maybe even IFTTT, etc in one fell swoop would be a nice start to make it easier to tie in. Since you're into python, something like node-red might not be bad either.

There are lots of other process managers that could fit well with agents as well, python and not that could be reasonable bolt-ons or extensions.

I'd be very happy to check out the best agent orchestration architecture you're referring to, email is in my profile if easier :). 1

In terms of open sourcing, I don't think anyone would have an issue with .NET, I wouldn't. Many businesses have exposure to Microsoft 365 already and using Azure, kind of a massive built in audience.