One thing I would like to note assuming your still working on the sequel, having the wings make you faster is not helpful. Generally in bullet hells, it's much more important that you can make small movements to slip between bullets so going faster only makes it harder to dodge.
If I could make a suggestion, you could make the wings unlock 'focus mode', a feature used in most bullet hell games that makes your hitbox visible and makes you move really slowly for easier dodging. Upgrading wings could increase the amount of time you can use focus mode.