I had this same exact consequence idea in mind but my teammates shut me down D:
You seem to have made that concept work great as every upgrade also contributes to your own demise! However, in terms of gameplay loop and pacing, I felt that the game starts way too slow as I didn't start seeing enemies on my screen till way farther into the game.
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A mix of them spawning too far, your projectiles flying too far (makes sense though cause you do want them sometimes ricochet back at the player), and enemies spawning with low HP. This picks up later but early on I felt like I was just spawn killing everything. Them spawning too slow and the density of them is probably also a factor.