I just finished making a Kato 11-109 into a small boxcab locomotive for my Maintenance of Way train. The difference between chassis, as far as I can tell is its length and number of wheels, as well as styling. The motor of the 109, which I am going to assume is common between all chassis, is a coreless DC motor, long and narrow. I'm most used to seeing this type of motor with an offset weight used as vibrator assemblies. My 109, despite only being two axles, is surprisingly strong! It pulls its 5 car train up a 3% grade with no wheel slip at all. I haven't tested its limit, but it could probably pull more. Just like all Kato products, they're very well built. Converting it to DCC using a Digitrax decoder was extremely easy. I'd highly recommend them for what you are trying to do, and am excited to see updates if you go through with it!
Here is a link to my post about my boxcab if you're interested:
https://modelrailroadforums.com/for...-designed-an-n-scale-boxcab.35736/post-567226
Edit: One last thing to take note of is that, at least on the 109, the coupler assembly sucks, and I don't say that lightly. Even the stock Rapido couplers kept falling off. I upgraded mine with Micro-Trains body mount coupler assemblies, but it took some modification, super glue and a lot of curse words. I'm still not 100% certain my mods will stay attached either.