It's a long shot, but here goes..
Ewing wanted to use Ross for the USAvengers team as Red Hulk but was told there were plans in place for him already. He's depowered, so, he'd be available for repowering. Why would they pass on bringing back Red Hulk who was fairly popular? They went ahead with a Red Hulk, so it's not on the basis of them not wanting a Red Hulk (if that makes sense). By this point, Banner was slated for death, so he couldn't have been saved for him.
He's not being used as an antagonist for Jenn, which leaves Cho. He doesn't have any real rogues and it'd be one way to carry the torch from Banner to Cho. Would Ross go to illegal lengths to accomplish his goals? He's done it many times in the past -- working with MODOK twice to get power and revenge.
Who would be in a position of power to start up a Weapon X/H program? Who has incentive to try and get Hulk powers again? Access to years of gamma research? Etc.
The Weapon H hybrid is gray. It's weak reasoning, but alternate Ross Hulks have been gray in past depictions. Also, the gray suggests darker intentions and age.
Furthermore, making the hybrid a generic person misses out on a big opportunity. There's a better chance of the character sticking around if it's someone we know, someone with a history, etc. In other words, compare it being someone we know versus a nobody. There's less work to get it to stick, and the concept is already ridiculed -- give it a history, motive and tie it to the other characters and there's a reason for the crossover, as opposed to just doing it cause it looks neat.
That's as good a guess as any at this point.
And the cover to Weapon X #7 is COOL homage to the CLASSIC (and always awesome to see) cover to Hulk #340!
I miss Dad & Dan.