An expanded universe in style of Hollywoood blockbusters from recent years isnt an universal key to the success. IMO Star Wars, all the superheroes things and even Star Trek have become enormously watered down on quality, because creators in the goal of trying to keep audience around decided to build around these established titles. And thus I wouldnt want to see DW getting similar treatment; the tv series and what already has grown around it is enough.
Doctor Who
A good old fashioned Doctor Who Community
I think the trick is to have it so you don't have to watch the spinoffs to understand what's going on in the main show. That way, casual fans can just ignore them, instead of being overwhelmed.
The MCU started out that way-- you could go into almost any individual movie blind and still understand what was going on-- which is what lead to its wild success. But then they lost sight of it, which is why it's been flailing in recent years. Disney Star Wars never understood it at all: hell, they don't even have a main series any more, it's all spinoffs, all the way down. Hence the whole thing feeling like a jumbled, chaotic mess.
Will RTD understand this? I think so, given his track record. He was pretty good about keeping it so you didn't have to watch Torchwood or the SJA to understand what was going on in the main show. Hopefully he keeps it up in the future.
I still want a Madam Vastra, Jenny and Strax spin off
This is the only acceptable answer.
I have an idea for a show I'd call 'Great and Bountiful' which would chart humanity's first major steps with alien species that don't result in the doctor having to interceed.
While I love Star Trek as an aspiration, I'd actually offer up Stargate as an example of 'humanity gaining access to alien tech and slowly improving'. We know from the lore there is a mass migration to the stars eventually, but humanity in those early years would be great.
One of my favourite shows RTD has done is Years and Years, while I would want a Who show to be that cynical, it would certainly be an interesting take on things to strike that storytelling format.
tbh what I would love most would be an 8th doctor series, but I think that's unlikely, but I have heard rumours of new animated stories with classic doctors, however I can't say how valid those rumours are. In terms of a realistic spin-off, I've heard about the Unit thing. The wackiest spinoff would have to be a Frobisher the Penguin spinoff, if they're bringing back Beep the Meep, why not Frobisher as well?
I want to see The Turlough Show, where every week for half an hour Turlough tries half-heartedly to murder the Doctor over and over, but always ends up falling into his own traps like Wile-E Coyote.
No specific ideas, but I am hopeful that RTD will hit it out of the park, and do it naturally. The Torchwood and Sarah Jane Adventures era of DW is still my favorite, and it did exactly what everyone expects and wants from shared universe storytelling before it was "in".
Tales from the Security Kitchen - who doesn’t want to learn more about the Security Kitchen? For example, why is there a security kitchen?
No Complications - explores the back story of that one Ogron who speaks English much better than the others.
The Adventures of Belal - The doctor’s little sidekick from Death to the Daleks in a series of adventures involving various menacingly tiled floors.