Does this issue have any affect on the potential for Unity support since Unity uses its own C# runtime?
Also, is there any progress? Its pretty cool that you're trying to support Mono. If you get the solution you're describing working, I suppose you could use Ultralight on pretty much every single platform with a C# application...including mobile devices? You'd just need to provide a platform-specific window for context and then display the Ultralight pixel buffer in it, correct?
I know a lot of people are flat-out sick of flakiness (and Microsoft's attitude) with WPF and UWP, and they are wondering why even use platform-specific tools anyway if they can find something else.