In Mechadgodzilla's first original appearance, he was disguised as Godzilla, so it's possible that the Godzilla we see in the trailer is Mechagodzilla BEFORE his pseudo-skin is destroyed

And then the remainder of the movie could be Kong vs. Mechagodzilla or G&K v. Mechagodzilla

Mechagodzilla is an alien

There are points in the trailer around 1:55 that show Kong and Godzilla on what appears to be either another planet or an area with some sort of spaceships (could be a flashback, not sure)

But this has to all be connected to Mechagodzilla's presence.

"we need Kong. the world needs him to stop what's coming"

They were already aware of Godzilla's presence. Godzila wouldn't be "coming"; they have a new enemy (Mechagodzilla) and retrieved Kong to fight him.

We see "Godzilla" plow through the naval ship around a minute in.

But historically, Godzilla has been pretty good about avoiding civilian ships in the water because he knows they're allies.

Especially if they aren't bothering him

The original Mechagodzilla was NOT skilled at hand to hand combat to the same extent that the real Godzilla was, so that could be why Kong's whooping his ass if that's Mechagodzilla.

The company that builds Mechagodzilla is called Apex Cybernetics #GodzillaVsKong

Other variations of Mechagodzilla's origin suggest he could be manmade, so that could be what we're looking at for this particular movie?