Custom router bits do exist for the track groove profiles, which suggests that SOME folks are doing it. I've always wanted to create some custom pieces--my siblings and I growing up played with Brio far later than the expected ages, as we were all railway nerds, and frequently mis-used the degrees of freedom of track components for wildly more complicated layouts spanning rooms.

Nowadays one of my nephews ended up with lots of generic track (gifts from uncle: me) and some very specialized custom switches cast out of resin by his maternal grandfather. There are multiple ways to solve the problem!

Lidl and Ikea wooden tracks are pretty cheap and mostly compatible (you might have to file the joints a little, otherwise they can be hard to attach and detach).

Lidl & Ikea tracks give a feel of cheepnis. I haven't stopped to properly contemplate why it is so. Maybe some sanding of edges would help - Brio are much more pleasing to the touch.

Yes, Lidl and Ikea tracks have rough surfaces. Brio tracks feel more polished. Or maybe they are just made from high-quality wood.

If it’s just edges, routing existing track with a round over bit is nothing. Maybe not much of a challenge though.

A friend has 3D-printed custom duplo and lego tracks. Not sure if she's also done it for wooden railroads. I haven't but I could really use some track pieces to adjust between common length and width differences. We've got several pieces that have two sets of track next to each other, and they all have a different spacing between the two tracks. Very frustrating.

We’ve 3D printed a lot of special tracks. Crossovers and splits, bridges, etc. It was really fun, and my kid pretty much always incorporates all of them into whatever layout we’re working on.

i don't suppose you have designs posted somewhere ?