It seems to be this was also a back door pilot for the Unit spinoff. I wonder if Donna will actually stick around for it? May she and her family will stick around for new stuff. I’m guessing if that happens Tennants Doctor will always be off doing something and that why he can’t help.
I’d be willing to bet that if they do a UNIT spinoff, it will be a special detachment with a specific mission, and Donna will only appear in cameos. Kate Stewart might be like an Amanda Waller, monitoring their progress from HQ and only rarely getting directly involved.
With the amount of focus it got in The Giggle, the HQ is absolutely playing a big part in the spinoff. They made a whole robot character who appears to be anchored into the HQ, and since the robot served no purpose whatsoever in the plot of The Giggle itself, the only reason to make the robot is because it will be a regular part of the spinoff. Therefore, the spinoff is going to be centered on the HQ we saw.