Theoretically, theres no reason to "block" the legacy signal in order to run your conventional trains.
As long as the legacy base is on, the legacy equipped locos will "see" the legacy signal not move unless they are addressed.( if they legacy base is off, legacy locos will default to conventional operation)
You can power your legacy base first, then bring up your CW 80 throttle and run your conventional stuff.
As far as varying the CW 80 with your remote,Lionel is way ahead of you on this:
A Lionel TPC unit as mentioned above. These are older but work well. Most likely you'll have to find one on the second hand market.
Or a more recent version of the same thing, the Legacy powermaster
The same rule still applies. In fact, it is possible to run conventional locos and Legacy cc locos on the same track with the same remote with a TPC unit or a powermaster.
The legacy loco performance will be limited by the lower conventional operating voltages, but this does indeed work.
