The Ace character is simultaneously the best and absolute worst wingman in the entire universe. They learn how to flirt with people through observing their polycule and then flirt with other people outside the polycule blatantly as both research for character types and trying to hook them up with one of their partners.
When the polycule finds out there's an internal conflict because one side is all for it, the other side is like "Uh isn't that like morally ambiguous and a little misleading?" And while they are arguing, the ace character has already made a bet with the aro character that they can land a new member before the aro character can, and the aro character is extremely competitive and they end up accidentally tag teaming some how and gaining two new people, one highly on board one a little confused how they ended up here but very enthusiastic and willing to explore.
And while the polycule is processing this information, the aro and ace characters are arguing semantics about who won the bet and one tries to say "Who can get the most partners wins" and the polycule IMMEDIATELY puts a stop to the impending orgy argument because they agree that while a big party can be fun once in a while, their schedules are too chaotic to add that many variables into the equation.
The aro character realizes THEY are in charge of scheduling and finance surrounding these things and immediately comes to their senses like "Oh yeah no that's a logistical nightmare I am NOT signing up for." And the only way they can talk the ace out of trying to do it for science anyway is reminding them too many flirtatious convos happening at once means they can't get it all down for research in the first place and the Ace reconsiders their stance almost immediately after.
Someone (not in the polycule) sets their sights on the ace character (not menacingly), but the ace misread ALL attempts to flirt with them as this person trying to help the ace character's research. Like it started out as a team up for some reason and they fall for the ace and want a physical relationship, but any attempt to convey that completely fails - even outright stating it. (I have watched this happen.)
Flirting -> Scene building help, fun banter
Confessing -> workshopping how characters respond, actual critiques given
Pinning against the wall -> OMG your eyes actually DO dilate this close!
Holding chin and tilting up to look at the other person -> Oh your eyes actually shook a little when your gaze flickered down towards my mouth and your eyelashes fluttered slightly. Kind of conveyed a hesitation like you're not certain. That's a really cool detail! I'm absolutely making that a note for blorbo #1. Do you think blorbo #2 would make an involuntary intake of breath if blorbo #1 leaned in? Oh if it was omegaverse that could be an opportunity for the pheromone factor to really heat things up-
Telling them some spicy things they want to try with them -> Ooouuu I need to tell Aro that move. I think they and genderless furry could really build on that idea.
Straight out saying it -> Oh that would be a perfect response to get blorbo XYZ to realize there's a miscommunication trope going on. But the plot device B would totally screw that confession up.
The entire time this is going on the polycule is slowly noticing this happen and watch like hawks to make sure this person doesn't overstep, but they are relieved to see they remain respectful if not completely frustrated and consistently confused by the failure to get their meaning across to the ace character and then one day one of them approaches the ace character while they are hanging out with this person, and are openly affectionate with the ace who reciprocates, and the person trying (and failing) to ask the ace out stiffens for a second and starts asking questions and finds out the ace is in a polycule and they sit there like
And I'm not sure if it would be more entertaining for this person to
Get invited into the polycule by one of the other polycule members, finds out the ace is still not fuckable territory, suffers while also being happy
Not get invited directly but has to figure out how to ask to join and the polycule don't help them, they just watch them struggle to ask the ace character, grinning evilly (they get off on it)
Gets invited by the ace character to fuck one of their polycule members, and discovers first hand the insanity that is this entire group, and the ace is INSUFFERABLE about getting another member to the aro character who is all but peeling their skin off to not be competitive back because they've already established too many people is too difficult for the aro character to juggle in the calendar and financial spreadsheet they run.