Oh, there are many who have ran this team, or a similar one. I more often see a BA running with a Sunflower than x3 Sunflowers though, usually with a Ruby Droplet or Magical Crawdad as a third. While the cheese factor of this sort of team is incredibly high, it can give some players an edge. The one problem with Sunlight teams in general is there are a few pets that can solo your entire team easily. Three examples are:
Xu-Fu/Kovok - They may solo most, if not all of your team. May get lucky with a Solar Beam takedown, but chancy because they both hit hard (Kovok will with BC), and can heal, which is boosted by the Sunlight weather. Being a sitting duck for three rounds against Xu-Fu is suicide, so if it doesn't kill him that is one SF down, and it also gave his Feed a chance to come off CD for the next one.
Emperor Crab - He WILL solo your entire team if he is running with Surge. Will take a while though.
Frog - Any frog with greater than 268 speed (in the case of the BA), or 257 speed (in the case of the SS) and Frog Kiss will wreck you solo, and do it very easily and quickly. FK ramps up to do 500+ dmg per hit against elementals, with random polymorphs thrown in there for good measure, and he can heal himself just fine. Technically, he could switch the weather on you as well but I mainly use them to counter Sunlight teams, so the weather would just get switched back to Sunlight on the next swap-in, and the sunlight helps the frog's healing anyway so may as well leave it up. You can keep retreating to the backrow to heal up, but the lost turns begin to add up and the frog's dmg is too much even for a boosted Photosynthesis. If I run into a sunlight team more than twice in a row, I stick him on my team and give him a sunlight referenced name just to announce that the cheese-fest is over
There are other counters as well (a Darkness comp with say x2 Scourged Whelplings and a crow for the Crawdad-Noc Strike isn't reliable here against the elementals though), and a few stalemates (a triple Imp team should be able to last forever against a sunlight team just using backline heals from Immolate), but the 4 pets I listed will make short work of a Sunlight team, and they don't need the rest of their team to do it.