I think they should unite the World and WWE titles. I'd also unite the Tag Team and Women's/Diva titles as well. One top man, one top team, one top women, and they can show up on whatever show they feel like. I'd keep the US and IC titles for midcarders you want to elevate.
I also wouldn't mind bringing back the Hardcore title for Raw/ECW when they start touring togeather, and the Cruiserwieght Title on Smackdown to differentiate the brands a little bit.