According to the fan site Alien-Covenant.com, the two horribly fearsome aliens in Alien: Covenant, the white-skinned Neomorph and the classic Xenomorph were supposed to fight one another in the movie.
Ridley Scott has, or possibly had, some very lofty plans for the Alien franchise following the release of Alien: Covenant.
Heading into 2017, Alien: Covenant was arguably one of the most highly-anticipated sequels in a year absolutely crammed with big sequels.
Since the Neomorph was a precursor to the Xenomorph, it would have been seemingly worth showing on screen how the Xenomorph is superior.