thanks mediajolt, glad it was helpful! In terms of baking, I think it would be a fairly vanilla process... I'd probably hook up an emission shader to the color, roughness, and bump (to get the pure color information), and bake out any maps I needed separately, to import into unity.
However, using vertex paint to blend textures is a technique that is much more common in game engines! I realized it could be done in blender after browsing some art from the most recent assassin's creed game. After some googling, it seems that Unity definitely has all the tools for creating such a shader. Here's a youtube video I found with an example:
https://www.youtube.com/watch?v=HDXwSEUYrbI
Also you can see the developers of Escape from Tarkov use it in this developer diary, at the 2:30 mark.
https://www.youtube.com/watch?v=vof9Fquazxs&feature=youtu.be&t=151
I don't know the details of creating such a shader in unity personally, though I imagine it's much easier with the new-ish shader graph. I plan on jumping into some unity stuff in the next couple months though, so if I figure it out, I'll let you know!
