The concept wouldn't bother me on a personal level since I don't ship Starco, but I guess it'd feel like a bitch move to pull on the fanbase and would make a bunch of the shipping episodes feel even more pointless in retrospect. It wouldn't make the show actively worse, but it sure wouldn't feel like the journey was worth the destination either. I'd probably just post on /co/ that it was lame.
Even though I say I don't ship it, I feel like 99.5% sure it's going to happen, I'd even say before the middle of the season, and I don't have a problem with it either. Shipping just doesn't really interest me. It just seems so obvious they're going to get together that I don't believe that scenario will happen, and at most I can see them doing the dumbass twist where Marco's related to one of the pre-Festivia royals so that he's technically a distant "Butterfly" but still not related to Star.
Also I just really doubt Disney would be in any way okay with Star and Marco kissing and thinking each other is hot and all that, only to go "o no that wud be incest, we cannot fuck :(" at the last second. Like they crossed that line a while back already