Okay, I see what you are saying, and in the case of JMC at Ryan for example it is becoming increasingly possible.
The first step down the road was to harmonize the procedures and checkrides so that they are virtually identical between the two airlines. Airworld and Ryan were doing that but when those arrogant tossers at Flying Colours stuck their noses in they screwed it up for 2 more years. They are just finally unscrewing what that lot or morons did.
Anyway, then you cross qualify the checkairmen (which is currently going on) or else you have 2 checkairmen sit on one ride. Then you get 2 pieces of paper (One UK and one USA) and snap you are done.
The license is a seperate one time hurdle faced by both sides but once done, you are there, and it is very easily done as a newhire.
Incidentally there are NO visa requirements for operating in and out of the USA, even from a USA base. The only time a visa would be required would be for domestic services, unlike in the UK where we all had to get A.L.E's (handled by the company so transparent to the pilot).
But it requires planning and giving your overseas partner a voice in how you operate your aircraft.
Incidentally, you can run newhires through the simultaneous program as well, just makesure all boxes are ticked.
That lot down in Miami are a bunch of scabs and have multiple problems. One is the mentality, two is everyone knows about the mentality. Therefore nothing will move quickly for them, and the normal pace of the FAA/CAA is glacial at best.
Cheers
Wino