So, quite some time ago, I posted a mod called Unlock Multiple Units. It works by setting the transportVehicle.multipleUnitOnly flag to false.

That is potentially going to mess with your mod, if it is loaded before yours is. Users may see vehicles being loaded, with the passenger multiplier applied, that they had expected to see with the MU multiplier applied. Some users, understanding what's going on, may be expecting exactly that outcome, however.
Not really suggesting you change anything here, just letting you know so you are aware, in the event you get any questions about how particular vehicles are being treated. This is, unfortunately, one of the few cases where load order does matter, as two different mods are changing the same characteristic of the same file(s).

One thing you might want to capture however, is the case of single units that are powered, but which also carry passengers (or anything else, for that matter. Anything that is powered, but which carries passengers or freight, is automatically forced into the MU menu, even if it is operated as a single vehicle. The stock Roterpfeil and M300 units come to mind.

Just to make your life really complicated, as an exception to the above, you'll probably want to ignore vehicles that are configured to carry a single passenger (4 or less in the model file.) These are almost always to allow the modder to place random numbers, or other random features, on the vehicle, and not representative of an actual carrying capacity.