If we're not using any CDN and disabling the file by default, then this will ...

If we're not using any CDN and disabling the file by default, then this will be great to add utility classes for site builders. The main issue is with CDN's, they disturb the performance of the site. Disabled files will also not impact the performance. In my personal opinion, we should provide utility classes.
The naming of the utility classes should not disturb the present theme. Otherwise, it's good to go.