>>56432344That's like saying Blissey should have been a separate evolution line because aside from having a pink egg-shaped body it and Chansey have nothing in common. The same logic applies to Mismagius and Midreavus, Weavile and Sneasel, and almost every other cross-gen evolution.
Alamomola looks like a textbook example of a "it just gets bigger" evolution: pink heart-shaped fish evolves into a bigger pink heart-shaped fish. The fact that they aren't related is the weird part.
While I don't have concrete proof, I strongly suspect Alamomola started out as a design for Luvdisk evolution, but got made into a single-stage line when it was decided BW would have no returning pokemon. It seems very unlikely for the designers to have made a pokemon so obviously designed to be a bigger version of an existing single-stage pokemon, especially when you consider gen 4 had a bunch of new pokemon that were evolutions of previously neglected single-stage mons.