After many hours of research and troubleshooting, I've finally found a workaround that allows me to control The Legend RE with my controller, both in Reason 10 and Pro Tools. This also works for Antidote RE, as far as I can tell. For the sake of anyone else having a similar issue, I'll describe the working configuration.
1) Setup for control in Reason 10. The only way I've found to have persistent control mapping of Legend (meaning I never have to reassign control parameters when opening a new instance of The Legend RE) is to alter the Reason .remotemap file specifically dedicated to whichever controller you've chosen during setup. In my case I had to find and edit the .remotemap file Reason uses to load the control map for the Akai MPK249. On Windows 10, the path was C:/ProgramData/Propellerhead Software/Remote/Maps/Akai/AkaiMPK249_402.remotemap.
The Legend RE manual has a list of available remote map parameters in Appendix C, but If you don't have that list you can obtain one for any rack extension by opening an instance of the virtual instrument and selecting "Export Device Remote Info" under the file menu and saving to a location of your choice (open with WordPad on Win10). You'll need to do this anyway in order the get the information you need to define the "Scope" line of any specific remote map. You then follow the remote map format to define the Scope and assign the knobs, faders, or switches to any specific remote map parameter found on the list. Everything needs to be entered accurately or the .remotemap file will not load properly. This is the best youtube tutorial I've found on the process:
https://www.youtube.com/watch?v=ALBdIkdF8fEWhen done you should have full, persistent controller functionality of The Legend RE in Reason 10. As a side note, your controller's MIDI CC values will need to be mapped to the recommended default values for Reason. My controller had a preset specifically for Reason with all the correct CC values so that is what I used and it works fine.
2) Pro Tools is entirely different though. Hard coding the remote map information into Reason's .remotemap file did not allow me to control The Legend RE directly when rewired via Pro Tools, but as far as I can tell it opened the door to allow me to use the MIDI CC values directly from my controller for control. So at that point I just created a new preset on my controller specifically for The Legend RE and assigned all my control parameters with the CC values provided in The Legend RE manual. Then it's just a matter of switching the controller's preset when using The Legend RE in either Reason or Pro Tools. From what I can tell, the ability to assign MIDI CC only became available after I edited the .remotemap file to include The Legend RE's map information. In other words, in order to get it all to work in Pro Tools I had to program it twice, once with remote map and another with MIDI CC (and potentially a 3rd time if you don't have a preset for Reason's default assignments already on your controller).
I hope this helps anyone struggling with the same scenario, as the information in the Legend Rack Extension manual on this subject is minimal, incomplete, and misleading. And in regards to customer service with Synapse Audio, I've been struggling with this issue on and off for almost six weeks now, sent two emails to customer service, and posted in this forum under plugin support almost a week ago. I got absolutely no response to either email or forum post. I know that customer support for software is generally bad, but for comparison, I emailed Blamsoft about MIDI CC support for their Viking VK-2 and got a helpful and complete response back in 10 minutes. Not even kidding, 10 minutes!! While I don't expect 10 min to be the new precedent, there's clearly a large discrepancy between Blamsoft's 10 minutes and Synapse Audio's 6 weeks and counting....
Please make the world a better place by caring about and helping your customers. By the way, I still have no answer as to whether I can get a crossgrade to The Legend VST if I email you my Propellerhead receipt.