To kick this off, here are a couple of small ones:
1. Make it so Whispaw becomes Coroona through levelup instead of Fire Stone. For one, we already have three 'Mons that evolve through Fire Stone--Vulpix, Growlithe, and Eevee--another one is a little redundant. More importantly, Whispaw, if I remember right, is first encountered in Coalchar Forest, very early on. If Fire Stones are available in Topaz at the same time they are in the canon games, the player won't be able to get them until very late. Starting around the 30s, Whispaw starts learning fewer moves, and Coroona starts learning exclusive ones. The player might not get the necessary Fire Stone until their Whispaw is in the 40s or higher, missing out on the moves it would've learned as a Coroona to that point, and being forced to go to the Move Relearner to get them...if Topaz even has one. Making Whispaw evolve around Level 25-30 would remedy this.
2. With the new musical moves Topaz has added, Sing's name is pretty generic. Why not change it to something like Lullaby?