I think Eggwars needs clear early game gear, mid game gear, and late game gear.
I think you might be phrasing it wrong. There definitely is clear early game, mid game and late game gear.
early -> Iron (or Leather on normal)
mid -> Diamond/Iron
late -> Netherite/Diamond
Your problem isn't the lack of clarity with which gear belongs to which stage, there are 3 "stages" of the game, and 3 kinds of gear, you do the math, it probably could not be clearer.
The problem you seem to have is that the gear is too overpowered for your liking. I sort of understand that complaint for normal mode and Iron armor as it is possible to get Iron armor very early into the game.
Though here I do have to say that the early game isn't supposed to last very long, there isn't much to do in it, and because after the early game there is the mid game it makes sense for mid game gear to be available fairly quickly. Based on how many resources you can get from your generators early I'd say that the early game ends maybe like a minute into the game, maybe 90 seconds if we are generous, but anything beyond that is already the mid game.
And for overpowered mode? Isn't having strong stuff fast sort of the point? I mean: its called overpowered for a reason, its not exactly meant to be balanced, its supposed to be ridiculously overpowered. If u want balance play normal mode.