The whole idea of a mid card belt is Blue. It doesn't represent anything.
Build credibility. It's a trial run with the fans. It's accustomed for wrestling fans to believe in a wrestler who has what it takes to get a midcard title. A rung on a ladder of success, so to speak. It's a stepping stone. It's an opportunity to make your name, or rebuild it. Or when the titles mattered, it was usually a symbol of reassurance to fans that someone was getting a push. Like a signal for fans to "watch out" for this guy.
Also, they shouldn't merge the titles. They need to do the opposite and keep them separate. Build an identity for both and build them up as something prestigious. They were on a good track at WrestleMania 31, but some where along the line it dropped off again. I have faith in them keeping the titles on track, but they are currently far away from that.