If he lives I just hope the Deathwatch won't want to poach him later down the line, that guy is probably our Chief Librarian...or at least one to train the rest of them.
I hope whatever favor they want as repayment is something we'd probably do anyway, like destroying a Ork WAAGGHHHHH or aid with a Hostile Xeno group. Tho i'd not be opposed for sending some to the Deathwatch later, when our Astartes can actually survive a couple campaigns of theirs, Deathwatch Veteran's would be a nice addition to any Company or Honor Guard.