I have worked abroad for years. Got all paid by the company that got me over, but going all alone?
Maybe you should seek work for one of the up and coming builders in the US, like Dave Friedman in LA. Now that would be quite something! You would meet all the big guns in the guitar scene.
I haven't asked Dave yet, but I've asked a few of the others that I know - just not the cash in it for someone to take the risk of flying me over to the US (much as I'd do that in a heartbeat). I've also asked PRS and was talking to Peavey for about a year, but it all went tits up in the end. Cornford said it was great me doing the custom one-offs, but they had no requirement for anyone doing that. I've also known Jeff at Matamp for the best part of ten years, but that would never work out.
The thing with Dave Friedman is that our amps are along the same lines, so theres not much we'd bring the the table that the other doesn't already know and he already works with the guy from Metroamps anyway. Not that I'd turn down an offer to work with him.
I've also known Trace at Voodoo Amps for a long time, but again, I don't think he really has the need for someone to design amps and one off's with him - Trace is a killer custom-amp tech himself.
Peavey were quite unique in their Custom Shop with one-offs, but it looks like the economy killed off that idea that I was possibly going to be part of.