Does Boxlang have something similar to Lucee Virtual File Systems where I can write an implementation against an interface and I can then map it as a filesystem?
Not yet. We have the cbfs project https://cbfs.ortusbooks.com/
We are considering migrating this to BoxLang. There might be a compatibility module for adobe/lucee. As we prefer the concept of disks rather than uri, because you still end up with tons of code plagued with URI definitions and abstraction is lost.