> Conversations with some potential users suggest that they are willing to accept fixed class paths and module configurations, and thus a fixed set of built-in class loaders, and to use specialized class loaders only when that flexibility is required
I might be misunderstanding the level of difficulty of this, but I'm surprised that a custom location/locations would need to be out of scope.
I'd love to have this out of the box with Java. I know it's possible already with other tooling but it seemed complicated or came with downsides.