I have a few ideas for what you could put in Soul Chomper. (Not saying you have to put this in. I'm not that person. These are just suggestions. I don't even care if I get credit for the ideas.)
1. Infinite Mode - Fight off large waves of enemies with a small break every 5 rounds to get new weapons. Survive 'till you die.
2. Randomly generated rooms or seeds or something like that.
3. Throw-able weapons like a shuriken you can find and they stack up to 25 or something like that.
4. More modifiers - Broken Horseshoe, which gives you less luck for finding good weapons is one of the ideas I have for modifiers
5. Make poison deal damage overtime
6. Add a custom cursor or cross hair or whatever you want to call it
7. A boomerang maybe?