Yup, As you can read in the long-ago history of my saga with the Aster/LGB White Pass mike, the original drive was a simple splined coupling that ground itself round inside half a minute - TWICE! Once of each of two locomotives. The fix was actually taking back to LGB on their stand at the Nuremburg Toy Fair and dumping it in Wolfgang Richer's lap [with all the others], and tell 'em 'fix it!'.that would be very difficult as both motors would need to be geared to each other, and best practice would be to connect "early" in the drivetrain, preferable motor shafts.
Also you would want motors to be vertical I would think.
Better to power the tender, and get speed matched.... adding weight to the loco will just chew up the gears faster.
If this was the LGB-Aster one (metal boiler), it will eat gears on it's own.
The replacement gear train has held up well, but not only is this maximum speed with five cars, it's maximum speed,period. Just like the real thing, 25mph IS the stop speed.