Sorry. Hate to shoot stuff down :/. Keeping his current title is fine.
1. Titling Ari solely for Relationships thread memes that may not be relevant in a year or so is unfair. See what Davsto and Firebringer said. Reck's title is celebratory -- the proposed Ari title is a direct reference to something he seems to regret.
2. Ari is known to the other non-SE half of the community as the cheerful listmod who responds with smilies and politeness no matter how horrible things get. Mr Blue Sky describes a more well-known aspect of Ari. It's not ideal (IMO) but it's still better.
3. Ari is known to like song references. Mr Blue Sky always had 2 sides to it. Pays The Rent is just a current meme. Keep it in the Speakeasy.
I'm also fundamentally surprised some people who disliked Mr Brightside are now supportive of Pays The Rent?
4. Ari laughed at it when I asked. ENTHUSIASTIC CONSENT, GUYS.
5. It was already proposed a long time ago, and almost prophetically became relevant a year later.
6. Instead of referencing a specific event, Mr Brightside references a general sense of paranoia, which is something Ari has openly admitted to having. This isn't a condemnation or trashing him for something. It's a personality trait, just like "Mulch completely lacks patience", "LLD rages a lot", or "Cooldog is kind of a wanker in many ways".
Yes, it became relevant in Relationships, but as a manifestation of that character trait.
7. And on top of that, Mr Brightside better represents his personality than Pays The Rent (which doesn't describe Ari at all, there's no deeper meaning), and Mr Blue Sky (which is really just being happy in general). Ari CAN get upset, but in a way where he's actively trying to stop himself from getting upset, and it shows. That's Mr Brightside, not Mr Blue Sky.
It hits the triple whammy of Relationships thread, Ari's general demeanour around site, and a real-life personality trait of Ari.