Hi Ben,
I've just found this email from almost a year ago. Sorry for ignoring it until now. Given the date it was sent I think I missed it when it was fresh while I was on vacation.
Regarding the question, I have abandoned the work I was doing on getting cross-compilation for Windows to work since my employer decided a Windows build for the app we were developing could wait some time and tasked me we something else.
However, I see that Moritz is working on cross-compilation right now so I'll try get some time to see if I can get his approach to work for our use-case and give some feedback or help in any way.
Alberto