I don't think the different weight classes would really make a difference at all. If Rich strings together some good fights and shows he hasn't been broken by Silva, a third fight with him would be awesome. He would definitely stand a much better chance this time. I think after the first lose, he had the "it was a fluke" mentality and his head wasn't in the right place. Another fight would bring fireworks, no doubt. Although it would make me sad to see him get caught in a clinch again, hopefully next time he'll take it to the ground.
Still, as much as I hate to say it Silva is just a better version of Franklin. Franklin is known for his crisp, powerful striking along with slick submissions and even slicker submission defense. Silva has faster, more powerful striking, and a black belt from the Noguiera brothers in BJJ. Franklin needs to come up with a really, really good game plan if he hopes to beat Silva.