I would unironically love Spinner development. Dude is most likely out of anybody to betray the LoV. It's worth remembering that he's super into Stain's ideals, and seeing a "hero" like Hawks join with the league could go bad REAL FAST. Imagine at first thinking Hawks joined the league because he agrees with Stain's ideals, but as he sees more of him and talks to him more Spinner realizes that Hawks isn't in it for Stain's ideals, he's in it for Shigaraki's (which he is, because that's who he's ultimately trying to get close to.
Spinner could betray the league by selling out Hawks and blowing his cover to the world, making society think their #2 hero is working with villains. This would inevitably cause an uproar in society, and to capitalize on the confusion and chaos Dabi might also finally break the "Endeavor is an abusive father and his son's a villain" story to further fuck everything up. So what are you left with? The #1 and #2 heroes discredited, society in shambles and in need of a symbol, and the LoV poised to make a huge jump in numbers (if the #1 is such a POS one of his kids joined and the #2 joined as well, this will seriously embolden not only criminals but average people discontent with society).
And all because Spinner took LARPing as Stain too far.