SCP would be awesome!
I can totally picture an SCP researcher getting a Milliways door, then doing the responsible thing and leaving it open while they secure the area and notify their commanding officer.
I think the... "Cleaner" solution would be pick a dozen SCPs that could co-exist in the same facility and sort of ignore the rest.
Of course, the POV characters don't need to
know the whole list, or even how many there are. So you still get to add SCPs any time you feel like it.
Good sources for myths: A large fraction of the myths I know came from
this children's book. For something more respectable, Ovid's Metamorphoses is a great list of reasons to depose the gods. The epics are good reading for other reasons, but have a pretty low content of mythological information per unit time.