I reckon it will be based on onyx, cos there is a little is a little "hint, hint, *wink*wink*" thing in halo reach; the highest rank you can get a commendation to is "onyx" rank..... Whaddaya think?
Maybe he woke up at one point or another and got a jetpack, and maybe the giant structure is like the "giant alien artifact" like the one in the ice cave in reach?