9. Bring Back Torchwood
Torchwood is an anagram of "Doctor Who" and that is the greatest thing of all time, no debate. It was also a very silly (but sometimes excellent) spinoff of the show that first aired in 2006.
It followed the exploits of the Cardiff branch of the titular organisation, led by Captain Jack Harkness, as they defended the Earth from all manner of alien threats. This "Doctor Who for grown-ups" ran for two seasons and two serialised stories, before disappearing in 2011.
While not without its flaws, Torchwood provided more mature storylines within the Whoniverse, and introduced audiences to great characters like Gwen Cooper and Ianto Jones.
Although Captain Jack actor John Barrowman is a bit of a no-go these days, there's still scope to bring back Eve Myles as Gwen, and reboot the entire series.
Torchwood was an RTD project through and through. The organisation was introduced in his era of Doctor Who, he wrote episodes for the show, and he served as its executive producer.
If he wanted to expand the franchise again, then a new team of agents headed up by a returning actor would be of huge appeal to old and new fans alike.