I'm happy to chat and compare notes about how folks have executed similar projects.
Though the last time I did this sort of thing I definitely couldn't have used CSS Variables. That seems like a good solution for modern browsers with or without a compiler like LESS.
To be honest, we use LESS fairly simply for the things it provides like variables, mixins, and nested selector syntax. We otherwise haven't had a need to make our stylesheets much more sophisticated. So when project planning came around, we didn't ideate much on LESS-based approaches, and I bet we could have and found an ergonomic approach there.