I don't like special coil. Using Coil just for an accuracy boost seems like a waste. I could just run a Rain team. I think you want to use the attack boost too.
I guess it can be alright since he used Haze to counter Reuniclus. He did say Milotic was the weak link when testing it though. Especially with Scald being weakened. It also feels a bit redundant with Cresselia + Chansey.
Jirachi is completely fine on Sun stall. It works great with Scarf, has impressive resistences, has an amazing movepool, it can check a bunch of pokemon with its coverage. It also has Trick for Reuniclus or an annoying wall, and it can flinch things for Toxic Spike damage.
It isn't like Jirachi isn't going to survive a powerful fire attack without Rain, and it can take water attacks much better in the Sun. Water is one of the most common ways to deal with Jirachi.