^Actually I think the lineup at the start is
Zukki, Aika, Yasshii, Reina, Ai-chan, Sayu, Eripon, Gaki, Fuku-chan
Ai-chan is in the middle because she has two solo lines in a row.
Then for the second verse, it probably switches to the order in the gif:
Zukki, Aika, Yasshii, Ai-chan, Reina, Sayu, Eripon, Gaki, Fuku-chan
Same as Ai-chan in the first verse, this time Reina has two lines in a row.
I don't think you could really dispute that Ai-chan, Reina, and Sayu are the most popular, or at least the most recognizable members in the current line-up.
Does it "look cheap"? Maybe. But I don't give a damn. That doesn't automatically make it worse than anything else out there.
Zassou no Uta's expensive-looking PV can't save it from a stupidly repetitive chorus.
At this point, all I'm looking for is visual impact and fun. The dance and colorful costumes are a good step in that direction.
As for "looking plain", how flashy do you want for the dance shot?
Plus, we don't know what other crazy stuff they're going to stick in for the rest of it.