Dude! Very very clean.
I made it to wave 32 and was very much loving how my Chief had grown. (Chief go BRRR, hehehe)
I don't think you need to give Chief less upgrades. If anything, randomly getting a 2nd one right after the first felt frenetic and kept me on my toes!
If you added way more enemies sooner, and got the player closer to death more times, it would've really increased the thrill.
Also, I would love it if ammo and health packs dropped less frequently (but only after you hit a cap of 20 or so. Then it would spike the players attention when they actually got low when they had to throw 5 to the chief and use 2 themselves. GMTK has a great video on game economies on their youtube.
Very Stimulating, wildly clean, great UI, just impressive all around.
Don't be afraid to use GMTK's team finder brotha! An audio artist and a visual artist (for FX and Enemy variety) would've probably gotten me to play to level 50 or beyond.