There are some petulant people on this thread.
Some people are fans of Hull first. Some people are fans of the game first. I am of the latter, but do not begrudge the people that put their club interests before the game (it's a hobby after all). I find it quite pathetic that some of the people in the other camp are taking some kind of superiority stance in not going to see their rivals play.
If it was a good deal, I'd go see Rovers play. I love me rugby, I'd have an emotionally attachment to the game (in the opposite way to normal!), the only issue would be price, where I'd stand and who I'd stand with. Doesn't make me any less a Hull fan for doing so.
However, I don't think it would be feasible beyond maybe a discount on the odd game, possibly a ticket discount for season pass holders against the likes of Catalans. Wouldn't be worth doing until the ground update is done as well.
I've said in the past as well that perhaps a KC double header would be a good shout one day. Hull vs Broncos and Rovers vs Catalans could sell the place out if marketed right, as well as generate a decent atmosphere for what is usually a dour affair for both clubs. Seems to work well in Aus, and union over here.