I'll play Devil's Advocate here...
There is something to be said about bringing the two together. *ducks rotten tomatoes* Now, just hear me out...
Looking at this from the POV of someone living in the States, it's hard enough to explain rugby to the average American, let alone explain to him that there are two forms (well, three if you count 7s) of the game. Here in the States RU is trying to get a foothold, but in some regions RL is gaining popularity. It may not be a problem in England or other places where both forms of the game are long established, but in the US with so many other more familiar sports (baseball, NFL football, college football, college and pro basketball, and now even soccer/football) competing for attention, dividing up the relatively small rugby talent pool between two different forms of the game will only serve to slow down its development here in the States.
However (and before I lose all board cred)...
If you did meld the two sports together there would be all sorts of problems. Firstly, the fans. 'Nuff said in that regard.
Secondly, club mergers would probably be necessary, and that in and of itself could get very messy. Thirdly, the two games very different in some very fundamental ways. Do you keep the union scrum? What about line-outs, rucks, and mauls? Which point system do you keep? How many players a side? And do you really want your dignified rugby union players doing that weird league fish-flop thing on the pitch to get out of a tackle? I mean, really...what's up with that?
There are a lot of things to consider, but in all fairness to sige, he's not the first one to come up with this crazy idea. Though most ideas about merging the two have quickly been shot down, there are have been experimental hybrid games played, though I don't think any of the hybrid forms have ever caught on.
das