I've had experience with Insteon systems installed in two previous homes and I'm about to install a system in a third home into which we just moved.
Looking over your system, Insteon can handle most, if not all, of the items. The reason I hedge a bit on that statement is that I have used Insteon for lighting, HVAC, irrigation (via contact closures), and limited access control/sensing (via motion sensors and contact closures). I have not fully integrated a system into a security system, though I understand that to be possible. I doubt fingerprint ID could be integrated, but it could be (especially if you can get a reader that will output a signal upon a true or false read to a contact closure). You can see more details on my system here
, if you haven't already.
What language/interface program would be suitable to my needs?
I feel confident that the ISY would handle all you want. I suggest the one with the most capacity, given all you want to do. Given your comfort with programming and tinkering, you should be able to do everything you want, assuming the hardware is there to support it. With contact closures and relays (e.g., the EZIO units), nearly anything is possible even when a function-specific hardware solution doesn't already exist.
As I said in another thread, the ISY has been rock solid for me and one of the best products I've every purchased and used. The support is great, too. The ISY has been updated continuously since I bought it 5+ years ago. I've updated occassionally, rarely NEEDING to do so. I suggest heading over to the Universal-Devices forums, if you haven't already visited there. The community there was very helpful to me early on. I haven't been active there in several years, but I wouldn't hesitate to go there again for help, advice, or feedback. It even has good participation by UD staff (where else do you find personal responses from the company's president?).