One with the two Victorian ladies could be good. Steam punkish and you could have Jack and the Silurian pop up from time to time.
That would be awesome.
I'd also like to see Torchwood 2, run by a peculiar Scottish man (who someone speculated was actually the 7th Doctor in disguise).
Dunno about that... Torchwood was pretty anti-alien in its heyday. Vastra as an occasional consultant, perhaps, if you could convince the people who wrote the Torchwood charter NOT to dissect her...
But the Silurians aren't aliens -- they're from Earth, aren't they?
Speaking of, I've always wanted to see a Doctor Who story set on Earth in the distant past during the Silurian age.