The TC made the consensus a while ago (more than a year) that we do want the external rules file that would be universal for any XLIFF 2.1 Fredrik was the proponent of this idea, and everyone agreed with him at the end..
If you look at the proposed conformance statement and the whole ITSM spec, we do care about both conformance targets. the XLIFF Agent that knows about the ITS Module, but also at the generic ITS Processor that couldn't of course make any sense of an XLIFF file without the external rules file..
Felix's AI is to work on the external rules file and he already proposed solutions for a few categories (target pointer etc.) I was just asking what needs to be stated at the extension points to have the ability to reference the external rules file (once we have it).
I think we didn't want to allow the ITS rules elements that would be needed to have the rules for generic ITS processors within each XLIFF Document.