Thought of a few fun ideas, hopefully this can be helpful:

1) Buttons/pressure plates mounted to the floor (or walls, either or), but with a minimum number of thiccs needed to trigger it. Could make for some interesting paths the player can use to progress, or to possibly give some players an added challenge on blueberry mode

2) Bouncers (I dunno the technical term, but those round and/or long pieces in a pinball table that make the ball bounce off when it hits) could make for a fun obstacle

3) Maybe a food mode where the sprites of the thiccs are replaced by various food items?

4) Maybe a weird one, but maybe a thicc battery (or capacitor, if you wanna be technically correct) where a player can charge it up to open doors, activate machines, etc. One could go around the level collecting thiccs, before depositing them inside to progress. Could also help to keep players from getting too big to progress through smaller levels or levels that make use of areas multiple times

5) Teleporters, could allow for some fun puzzles, challenge the player to remember where each one goes, or could just be a fun set piece

6) Cannons for players to hop into, to launch them really far in a chosen direction. Could add a challenge where players have to utilize them to keep their strokes low in number, or to spice up the gameplay