I know the first argument against this, that the suit was fossilized. Yes, because there's a good chance he found the suit and decided to wear it for piloting the ship, maybe the ship had structural integrity or maybe he wore it in hopes to contain whatever had ingested inside of him.
Second theory, covenant left us with David and a whole bunch of people in cryro tubes, and undeveloped fetus baby's,
Maybe thats where he got all the subjects to make all this eggs on the crashed ship? As seen in alien?
The reason the alien developed a bio mechanical look is because of hybridization or the original host was David all along? from the get go, procreation and creation was something he was kinds obsessed with.
We never actually saw inside of the suit in alien, so it could have been anyone inside it. Then there was the acid burn hole in the crashed ship. So whatever busted out clearly burned a hole to escape for unknown purposes.
I do think the mystery behind the crashed ship in Alien is fantastic and it leaves a lot to the imagination, but prometheous and covenant kinda already ruined the mythos behind it