I asked RTI if a table exists that could tell us which old remote programming could be simply squeezed into a current remote, and I also mentioned the Crestron issue. I got this reply today from Chris Pauly at RTI:
There is no table which currently shows what a device can be converted into.
However, Integration Designer can show you the information that you are looking for. First, open a System file in ID and select the legacy remote. Then go to the Device Menu and go to the “Convert Device” option. Hovering over “Convert to” will bring up a menu of the devices that your selected remote can be converted into.
I've never understood why customer service people, especially on the tech end, would not hear a question about this information and respond with "Let's put together a table so the installers don't have to do this -- they can make plans without having to crack open the software; they will see that we are interested in getting them the information they need; heck, we will have a better chance of repeat business if we give them tools specific to RTI product, tools that other manufacturers don't give."
As far as your Crestron compatibility concerns, RTI has a Crestron code set for use with our remotes. Any RTI remote which can transmit via 433 can use this code set to “talk” to Crestron’s 433 Receiver. Currently the T2x, T2cs+, T1b+ and T3v+ all have this capability.
Well, okay, but that wasn't the issue. The issue was that if the programming cannot be imported into a different remote, the work of organizing those commands and turning them into a working remote is lost.
So, while this is not a complete answer, it at least gives some of the parameters of what can be done.