Closing the loop on this thread in case someone references it later.
The only technically viable solution I found was through use of Toothfairy. Once configured, Toothfairy can be used with keyboard shortcuts to disconnect the trackpad on one Mac and then re-connect on the other Mac.
Technically it works fine. However, from a workflow standpoint it’s still klunky. For now, I’ll continue to have both trackpads on my desk. Much faster switching time!
The VNC approach is most appealing from a switching speed standpoint, however the Alfred and BTT limitations are deal breakers for me. I’ll keep tinkering, but for now I’ll deal with losing a few square inches of desk space. 
— jay