Welcome to the forum.

Your needs can be handled by a less expensive control system, like the TSU9600 and RFX-9600 extender. However, it is not something for the faint-of-heart and typically, I would not recommend for a beginner. I think some of the more accomplished remote programmers would have their hands full with your configuration.

RS232 is typically challenging, etc.

I suspect your Crestron quote was 2-3x the cost of these products, including custom design and programming.

If you are interested in having it developed professionally, drop me an email or call.

Dave