The cheapest option you have is to source a PMC3-XP from eBay. Only place I know of you can find one. They were discontinued. Then you need a crestron RF gateway (There are two, the one you need depends on the remote you get) - these are still made. Then you need the new remotes. Just about anything from URC or RTI will work, although I'd stick to the simpler versions. You don't need touchscreen or anything. Then, this all has to be programmed. From scratch if your original installer didn't give you the source code and is unwilling to do so.

Or you can get your original installer to create an iPad/iPhone/Android interface and you can use a small tablet as a remote. This would most likely be significantly cheaper. By a lot.

The MC3 is only for full crestron, not prodigy. Upgrading to the PMC3 won't do anything for you that you're looking to do. Still uses all the same equipment limitations. You would have to get the PMC3-XP.