I haven't been able to get over to the Geissele Industry Forum in a while, but I asked him about this about six months ago, and he told me that it could pretty easily be done, but that he was very reluctant to build a trigger that would require a three position selector that might cause a potential issue for a customer.
If he is reconsidering one, I'd definitely be very interested in it - I'm not interested in bump firing, or any of that non-sense, however, I like the idea of a good single-stage trigger that can be used for more dynamic shooting scenarios that could be rotated to a good two-stage pull for a little bit more control and precision. Basically a semi-SSF, with its two-stage semi-pull, and single-stage automatic pull, but again, obviously, semi-automatic only.
I'd suggested doing a specific selector as well that would only be compatible with the trigger, either in house, or through partnership with BAD, which, I think, could probably avoid any possibility of being hemmed up for having an automatic selector in a semi-automatic only gun.
A great option, I think, would be to set the selector up so that the single stage pull was at the 90 degree position - allowing for muscle memory to the 90 degree "flick," and then the two-stage pull at the 45-50 degree, so that you can "click back" for a more precise pull - kind of like an AK selector. You could even potentially make it into a four position selector for an "SSF II," giving you the capability to use the same lower for pretty much any purpose by just swapping the upper. In something like a CM901... it would make for an interesting system.
~Augee