As for the earlier subject...
Being "retired" from game design I have no problem "giving away" things I once thought of as "my best ideas". For example, making space hockey "on a pinball machine table". 10 years ago I never would have told anyone about that, today... I'd be thrilled to see some of this stuff actually used somewhere so I might as well tell them to people who might actually use them. This subject reminds me of another formerly "secret great idea"...
The "HyperSkip" drive. This is essentially a drive system and a cloaking device all rolled into one. Like a dolphin swimming near the surface and occasionally jumping out of the water to breath, a ship with a "hyperskip drive" effectively fades in and out of existence as it moves. Like dashes and dots, it "dashes" a distance "cloaked", and then it "dots" out of cloak for a much shorter distance than when it is cloaked. It can only fire when it is visible, and is hit normally when cloaked if weapons hit it.
What makes this so cool as an top down arcade ship is that there is a pattern to how this ship fights, using it's cloaked periods to make unseen direction changes and time it so you are ready to shoot when you are able to. It feels to the player like "coming up for air" every time they shoot.
Your ships are probably already worked out, but if you were thinking of adding more in the future you might try a "hyperskip drive", it would make for a very unique ship that has a specific pattern and rhythm to how it fights.