I too think the bit about throttling up it is to get action from the acc. and the locos are to fast while doing it; so he is going to power the action separately from both lights and track.
As mentioned, all units must be phased so you can combine commons.(I like the Lionel video on YouTube "Phasing two or more tranformers for use together")
This last transformer choice might be relevant. (so far, sound great)
The two Iso rail triggers would just deliver the missing common to the tower.
Using two or ten triggers at once poses no curcuit danger here (outside of heat if it never-ever sees off time and is set to very high volts.)
You can feed the action's hot wire source from any of the taps that use these same commons; but don't mess with odd voltage combos unless they feed a totally isolated circuit.(also worth noting some of those acc tap combos are not breaker protected internally and should be fused/breakered.)
(a relay is also a simple way to totally isolate the action fed circuit from the trigger circuitry on the rails. With a relay you could use a button cell battery to turn on a 440v three phase welder.)
You mention it is "far away". Is the wire used big enough to handle the draw of the accessory? Wire choice is about X-amps drawn over X-distance. Too light a wire for too long a distance won't improve much with more power simply being available; it also needs to be able to reach the item and still have strength there.
E.g.if. you simply matched it for twenty feet it might underperform where if you used a larger gauge it might work fine, with more of a snap and needing less voltage at the dial. (because distance on light wire = voltage drop too)
