What a cool concept, reminds me of Ikaruga which also had the idea that you don't want to be avoiding bullets all the time. Though I really like the idea here that you actually need to absorb the bullets in order to progress at all.
This is my personal opinion completely based on my own experience as a longtime bullet hell arcade player so feel free to take it or leave it - I would avoid or drastically reduce the startup inertia for the ship, and possibly remove the drag as well after stopping. The reason for this is that you can't design more intricate bullet patterns because dodging is imprecise. It's totally up to you and your design, that's just my 2c as a superfan of this genre. If you look at the original classic bullet hells - Batsugun, Dodonpachi, even Touhou - they never have any startup inertia or acceleration for this reason.
I also found it somewhat hard to control because the cardinal directions were rotating with the ship. I don't think there's anything wrong with this, but combined with the startup inertia it felt a bit sluggish for my taste.
Overall though absolute banger concept and great foundation to build a cool game. Really hard in a good way!