"This *is* a mess. Lionel will be going on 3 years offering high-end engines in its catalog for which it does not offer a controller."
I know delays are frustrating, but......Not to be unduly argumentative, there are much bigger messes. Just visit our Emergency Department any time in the last few years or your local funeral parlor. I know, inappropriate attempt at black humor. Point is, most of us have seen much, much worse than a year or two delay in some toy train product in recent years. And this delay isn't impossible or fatal.
I also don't think your comment is entirely accurate. The cab-1L and base, and even the 990 were still available at many dealers as recently as a year or so ago. I know because I bought them as soon as it was announced they were going bye-bye. That availability changed rapidly, but I think it's closer to a one year hiatus, than three, for most of us who delayed getting Legacy for a decade or so.
Practical questions. Have you tried the app? It controls every single Legacy function and is free. If you want a remote the $55 Universal Remote provides all the commonly used Legacy functions that most people use. Whistle, reverse, speed control, electrocoupler, horn. It's a bargain and except for really large layouts, its Bluetooth function is more reliable, in my hands, than TMCC, Legacy or DCS.