Be creative! Depending on how much you want to them to interact it could be anything from vm’s playing a mp game to segmenting a world into chunks and making them ignore each other, shouldn’t be too hard hopefully.
I kind of assumed that would have to be in it for basically the reasons you said, the main thing I can see getting at the pathfinding being really useful is large scale warfare and things like ambushes where going through one path or too close to an area can actually screw you up massively and where we could improve on the strategy that’s pre implemented using pathfinding.
I’ll try and think up some ideas for challenges and they’ll likely just be kinda basic things but for starters something project euler could work with a challenge of the day from it. As for experience I’m just a hobbyist that likes programming, I’ll tackle pretty much any task and because of it I can program. I’ve tried everything from writing scripting languages to n-dimensional mp computer games but really I just try whatever catches my attention and to learn new stuff.