The XXXX looks to me like a not-so-distant ancestor of Boeing's just-selected TX contender (it doesn't have a real type name yet as far as I know), on which they partnered with Saab. If there's a real design lineage here, it went dormant for 40 years which must be some sort of a record.
The design reminds me of some British projects from the 70's, mainly the P.110. Did BAe have any influence over this design? I know that at that time, they had been working together on what became the Gripen.