There are multiple ways to make aliens directly related to humans either with some nonhumanoid alien intervention, or with genetic engineering.
Firefly proved quite well there is no need for FTL.
I have thought that often in regard to the Betazoids, if they refused to give Deanna any sort of alien appearance (there are people with solid black eyes, it's a rare condition affecting the iris) they should have just made her an augmented offshoot of humanity. The whole culture of Betazed (what little we saw of it) was depressingly human.
The Nitzscheans on Andromeda were basically augmented human Klingons.
Firefly was a special case in that they had that engineered system with multiple, inhabited planets in "walking distance" IRRC.
It has been commented that humanoids are basic to Trek.

Greys would certainly be an intriguing variation on this theme. It would take Trek in a new direction.
I'm not an expert on UFO lore, but aren't the Greys supposed to be enigmatic, with an unknown agenda?
If we include aliens form UFO lore, then I also want some sexy, Tolkien Elf inspired Nordics, sneaky, subterranean Reptilians and something spooky modeled after the Mothman or the Flatwoods Monster.
What I know about UFO mythology the Greys are impassive scientists but it all seems to have been muddled since the whole thing started with Rosswell.
I think the word right now is that the Greys are operating some structure on the moon that catches human souls and forces them to reincarnate.....presumably for shits and giggles.