Warhammer 40k fluff thread VI: They see me Ward'en, they haten

[Wraith]

Kind of puts me in mind of the Mentors Chapter, though twisted around a little.

There would be a difference, in that the Mentors loan their squads out to other Chapters so as to be able to learn different tactics and battle plans and collect them together for their own reference. They basically go out, watch how the Space Wolves work in a battle, then pick out the bits that seemed to work best and use it in the future.

This new Chapter would kind of be the reverse - they get loaned stuff by the Ordos Xenos, test it out on the battlefield, and then report back on what happened for the greater good of researching new weapons rather than tactics.

That might work - an entire Chapter specially trained for using radical new weapons in major conflicts, using conventional support teams to get the job done when it all goes wrong. Mechanically you'd probably just use Codex: Space Marines and take other Marine Codices as Allies in order to represent the R&D squads that carried your 'experimental weapons'.

Either that, or play a Deathwatch army.
That's probably the most direct way - they are Space Marines who answer to the Ordos Xenos directly, so it wouldn't be a massive leap to suggest that a Radical Inquisitor had approached a small Deathwatch brotherhood and asked them to test out some newly discovered archeotech/artifacts on his behalf.