Please keep in mind that these comments are just my opinion, you are not being forced to do anything, rather, this is what I would change to this personally.

-Brainstorm other possible names for the pack? "Eggman Base" is a little too simple, and makes it hard to stick out when people are referring to your mod.
-Enemy spam in rooms is a little much, especially when I can see many robots taking out others just attempting to shoot at the player
-Tight hallways at the start are not necessarily a bad thing, but feel more like air vents compared to the size of rooms which open up
-The maze-like section in the beginning could be used more effectively to hide items such as shields, lives, or rings.
-Death pit right near the beginning might not be the best, as stated before.
-Rings need to be given the float flag
-More rings should be placed about to guide the player in the direction they should be heading
-Emeralds could be hidden in different places, for example, finding the green chaos emerald within the first minute of playing doesn't seem to make much since in general context of Sonic games.
-All seven emeralds in a single level may not be the best idea, unless you plan to turn this into a very long level with a lot of exploration.
-Adding colormaps to the water can be very helpful and pleasing to the eye, more on that [here] [https://wiki.srb2.org/wiki/Water_design]
-The use of 3 Eggman bosses in this level feels a little strange, especially with a horde of robots surrounding them in the level.
-The bosses can be skipped by simply going to the goal, if you plan to leave the bosses, or even a single boss in, consider making a door that opens only after defeating Eggman.

Overall this has potential, with several themed sections to the level with various platforming, exploration, branching paths, and more. As Sky said, read up on Level Design 101 and keep working at this idea.