Intel isn't really a single architecture either. You need to either compile for the lowest common denominator or detect cpu and other hardware features and enable or disable code accordingly.
Demand for arm is going up, not down, especially with these tablet/netbook combo deals out now. My interest for an arm version is primarily with Linux and single-board computers. I'm already a happy license owner for st2. You don't have to work directly on the hardware, there's an operating system under there that can handle some of this stuff for you. I don't know of a Mac OS arm device with a keyboard, but Linux and Windows and Android are sure busy with that.
Get on odesk and see what's out there for arm developers. I'm sure somebody is willing to sign an NDA, and some of those guys work pretty cheap. If I had the time I'd probably work on it for almost nothing, just to get an arm version out there.
The only way I can see this as overly complicated is if you write a lot of assembly code or bypass the operating system and try to access hardware directly. Frankly when you do either of those things, the app tends to be a single platform on a single operating system and never gets away from it, so I doubt you do that. Your existing ST2 code works well on Windows, Mac and Linux.
I'm not trying to be pushy here, but if your code were Open Source it would probably already work on most Arm versions, as well as ppc and some other bizarre stuff. I write commercial software for a living so I understand you have your license model and I respect it.