Never thought of that idea. I have installed several Tsunami's in smaller steams, but had always hard wired them. I'll give your idea a go and see what happens.
Installatiion of a Tsunami is very easy if you purchase a short wiring harness ($5) with an NMRA plug on one end and a JST plug on the other, because the 2-10-2 has the NMRA plug-n-play socket in the tender. The solder-in wiring harness that is on the Tsunami can be removed by cutting away a small amount of the shrink wrap, and the new harness can be used.
The only soldering required is the speaker.