I guess your team is a fan of Beatles music.As those of you who have seen my RMT would know (muh shameless self plug), I've been playing around with sun a lot lately, and I think a few Pokemon related to sun should rise a bit.
First of all, I'd like to nominate Victreebel to B+. While it's not really that useful outside of sun, Victreebel is a huge threat on sun teams. Almost nothing outside of dedicated special walls can switch into Victreebel, since Solarbeam, Weather Ball, and Sludge Bomb hits pretty much everything in the tier neutrally, and what can switch in (Lickilicky, SpD Musharna, etc) is crippled by Sleep Powder. There's also the possibility of it running Growth, which gives it serious sweeping potential. What holds it back from being A- worthy is the fact that it's only really good on sun, is revenged easily by Sneasel, and is outsped by faster scarf users even in sun.
Additionally, I could see Sawsbuck rising to A-. Sawsbuck is a lot like Victreebel in that it's really threatening under sunlight. However, unlike Victreebel, it's actually a good Pokemon outside of sun. While not nearly as good as Leafeon was (rip ;_;), Sawsbuck can still be a threatening sweeper thanks to its good Speed, decent bulk, and good STAB combination. Additionally, it can run Substitute in the last slot in order to set up on something that ordinarily counters it in Gourgeist (in a very similar manner to Sub SD Bouffalant, but better against offense). I'm not too passionate on moving it up, but I think it could be worthy of A-.
Finally, I'm going to suggest Carbink to B, although B- is fine too. Carbink is a great sun setter thanks to its access to Stealth Rock, which is otherwise exceedingly hard to fit onto a sun team, and great bulk, which makes it rather hard for most Pokemon to 2HKO, which allows it to set up both Stealth Rock and Sunny Day a lot more easily than Golem can. Comparing this to Volbeat, which is in B right now, both have equally useful niches as sun setters. Carbink can also run a decent Calm Mind set. I haven't used this set, but Detective Dell has used it and found it to be good, so there's that as well.
..........................................here are my thoughts:
Due to experience, Victreebel is a pain in the bum if you don't kill him before he sleeps ya, as well as being a good special attacker or mixed attacker, depending if you like knock off and power whip, or prefer to use him in the sun.
While I have not faced Sawsbuck in battle, he seems good under sun with Chlorophyll and also pretty decent for a non-sun team as he has sap sipper, giving him a free switch into grass types that like to use powder moves (watch out for Sludge Bomb Tangela, however). This in tandem with swords dance and good speed make him a threatening attacker even out of the sun.
As for Carbink, even if you plan not to use him as a sun setter, he's pretty decent, nonetheless. Not only does he have Stealth Rock, but he also has access to dual screens. In conjunction with Sturdy and defenses of a Shuckle-wannabe, he can get things done. Also he has trick room, although I'm unsure if that's a viable team strategy in PU.