I think regular (c4 & Nest) thermostats do work in a limited capacity with the Infinity system but will negate the variable fan function, which is the most people get the Infinity system in the first place. I've never tried it but have read past posts on this forum from members that have.
Also, there are a ton of drivers written for C4 that'll help with some of the things that you have listed here. Join the facebook Control4 page as well. I've had a bit of luck there though not as much as on here. There are some gurus on here that really know C4.