I know that the numbers were talking are unprecedented, but this is one of the reasons as to why I suggested Deathwatch. Their mandate is to capture xenos tech and give it to the Mechanicus in order to reverse engineer it - this is how the Imperium ended up with the C'Tan Phase Sword and such.Originally Posted by Cheesegear
An alternative is to go completely the other way - this new Chapter could have been created FOR the Ad.Mech. in order to do just this. Let's say they have inordinately strong ties to Mars - like the Iron Hands - and their determined role (in the same way that the Space Sharks and Minotaurs were 'designed' to fight other Marines, perhaps) is to perform high-level testing of soon-to-be-released weapons and equipment on the battle field and then report back on how well or poorly it went.
It'd look a lot better if your force was led by a Master of the Forge or Xenos Inquisitor, just for the flavour of the thing, but there's no more reason that a Chapter couldn't be unexpectedly trusted by the Ad.Mech, than one could be trusted by the Grey Knights (as with the Exorcist Chapter) and the likes.
There's a little bit available on the Lexicanum. They don't seem to be particularly well known or used, sadly.