Unifying the Intercontinental and United States Championship wouldn't be a good idea at all. When I found out that WWE would unify the two sets of tag titles, I wasn't too happy about it as I thought that this, "available to superstars of each brand" thing wouldn't be used in full effect. And during Carlito and Primo's reign... that was exactly the case. But now, I find the Unified Tag Team Championships to be a pretty good addition to the WWE.
However, it wouldn't work for the mid card titles. It's been a while since WWE has had an effective United States Champion and an effective Intercontinental Champion at the same time. I feel that Rey Mysterio and Kofi Kingston has the potential to lead the mid card for their respective brands for atleast the rest of the year. Unifying the titles when you have such great champions right now would be the wrong decision.
On the Raw side, you have United States Champion Kofi Kingston defending the title against all-comers. For the past 3 months, he's had title defenses against M.V.P., William Regal, Matt Hardy, The Big Show, Primo, Jack Swagger, Carlito, and The Miz. He can counted on to hold the title for as long as WWE keeps him fresh.
On the Smackdown side, you have Intercontinental Champion Rey Mysterio, who, during his 2 title reigns, have had fueds with Chris Jericho and Dolph Ziggler. Jericho being more experienced and more talented than Dolph Ziggler, has had a much better feud with Mysterio. Now with Rey Mysterio defending the title against Dolph Ziggler for the 3rd straight ppv, you'd think that I would find it entertaining. However, I feel that WWE can give Mysterio a better opponent, as I think that Ziggler would make a horrible Intercontinental Champion.
The mid card titles are about as strong as they can get at this point. Unifying the tag team titles was a good idea, and keeping them unified would be a good idea. That is not the case for the mid card titles. Maybe in the future, someday, but not anytime soon. They are just fine.