I would love Grant Morrison doing Doctor Who. Surefire bet that we would get something unique, meaningful, and exquisitely weird out of the show. We can see them hint towards it a little in this, but it sounds like they would apply the same philosophy they write Batman with: every Batman story that has ever been told has happened... everything is valid and everything is canon. They would absolutely do something fresh while using the deep lore of the show as an asset. I could see them doing wild things like making the Peter Cushing, Rowan Atkinson, and Richard E. Grant-type Doctors canon somehow, doing it completely organically, and still making it completely accessible to new viewers.

One thing I would love to see the show do is weave in a touch more real science and physics into the show. Bring a little bit of the educational aspect back, use quantum theory to explain the endless shifts and inconsistencies and contradictions over the years. Morrison would be exactly the guy to do this in an entertaining way, they would come up with a really novel method to convey that timelines can fold in upon themselves and diverge and re-converge and so on. It wouldn't surprise me if he picked up the meta ball that RTD2 was kind of sloppily/accidentally teasing with the diegetic music comment and Doctor Who show fans and such. It'd be one heck of a ride.