@Fleur de Lis
Cadence and Shining are fine in concept, they need major re-working to be interesting characters and to slot Cadence into the mythos properly but their useful characters to have on hand to add dimensions to Twilight as well as have a Younger Goddess to bridge between the new diety and the old immortals.
Also, with a few extra lines of dialogue you could work Celestia takeing an L to Chrysalis, like as Goddess of the Sun I could see her being like Head Captain Yamamoto from Bleach where he rarely fights because even a little of his power causes major collateral damage. So Celestia might be able to vaporise Chrtsalis with ease on a battlefield but in the middle of a city at a crowded wedding it would have done more harm than good. Also I think Celestia starting to heat up and Cryssy chastising her for not being careful with her temper would have been a great character moment.
Either way it needs more work to iron out the holes.
For me Canterlot Wedding’s real issues is it the first time the higher ups stuck their nose into the story for the sake of product placement, which would become a running theme and open the door for more corperate dickery as time went on.