Don't be so surprised. Hasbro does have final say in GIjoe stories because it still is their property being represented. I know they stopped DDP from some ideas when they had the title.
Also, remember, Hasbro made a few Kamakura figures as well as put him in Sigma 6 after being created by DDP.
Well, yeah I know Hasbro has the final say in just about anything, I've dealt with them on interviews that go through very tedious filtering, it just isn't much of a factor on their toyline. Kamakura also had the advantage of being built into the MARVEL Snake Eyes mythos and is still more the exception than otherwise.
Not saying it won't happen or can't happen, but it's not a simple as merely being semi-popular in a comic.