I could tell you wanted to make the game hardcore. My advice would be to seek inspiration from dead cells and dark souls, especially dead cells. Since in that game, if you die, no matter where you are, you start from the very beginning. But with your upgrades intact.
Also, if eventually you decide to not add checkpoints, you might want to make the game a lot fast paced than usual. Maybe make it so that players can fully explore or beat a section in less than 10 minutes.
Still, it's a great game. :)