Sam:
In addition to asking here, maybe also try asking Lionel (email): TalkToUs@lionel.com to see what they say.
And: From the instruction manual, page 14:
Use of multiple Universal Remotes:
You can use as many Universal Remotes as you choose on any one layout. You will be able to connect any three LionChief / LionChief Plus locomotives using the instructions above. Any time you power up the Universal Remote (after connecting to 3 specific locomotives) it will automatically connect to those three locomotives and you’re ready to run trains.
Maybe worth a try...
Stan