Hmm, the resulting Xenomorphs would definitely be threatening, although I doubt they'd grow to Kaiju size.
going by the movies, and comics based on the lowest common denominator regardless of host size (so long as its large enough to be a host) the resulting adult Xenomorphs tend to fit into a certain size range (was from dogs tend to be bigger than dogs but no bigger than the ones from people, and larger animal ones tend to be around that same size, give or take some environmental advantages)
It has always been a theory that I like that on their native world there are Daikaiju sized creatures that they can also be parasites for, and not be wholly fatal to them due to size.
Have this outline somewhere for a story about facehuggers crawling down King Kong's mouth, with Kong spitting out blood mixed with chest bursters later. The results are fairly large (for Warrior caste) but not gigantic Xenomorphs.
to do that, he must have been on land, as far as i know, godzilla only comes out of the ocean to fight other kaiju, or to destroy a city, i think it was a huge ass facehugger that got lucky (because godzilla could have fried it with his atomic breath the moment the face hugger pounced)
Aw sh%t someone call the Jaegers!!! Oh who am i kidding even with their help we're doomed! DOOMED!!! Oh and its a very awesome drawing I love the details especially the little mouth getting ready to vaporize everything with the atomic breath