I'm thinking about changing the processCSS gulp task that Aurelia CLI creates to create physical css files, instead of including it directly in the app-bundle.
Are there any major drawbacks within the Aurelia framework to doing this?
I'm more comfortable with separate css files after preprocessing, but I don't want to do it if I'd be missing out on some performance benefits, or create other troubles down the road.
I don't think there's any major drawback that can't be reasonably overcome. However, I would try to evaluate the benefit of doing it your way, instead of bundling it together.
I'll list a couple of points I can think of, in no particular order.
One last thing, it may be worth your time to experiment loading the CSS in different ways, including as individual files and see which way works best for your environment.