Since everybody loves this mod and gives their suggestions, I also want to contribute (because I love this mod and have some suggestions):

First, as the title says, I think it would be pretty cool to have some active items, like the mod has blue, green and red, but this time yellow/golden.

Like in TBOI, you would have crear rooms to 'recharge' the item, and I think it only makes sense to implement these 'charges' with the mana bar (because its also funny to only have 20 mana thoughout the run lol).

You can maybe charge 10-20 mana per room, start with 100 mana and have some items to increase (or decrease) this maximum and even a passive regen (which would be disabled from the start in favor of compleating the rooms).

This are some examples that benefit from this change, all these would be accesible from the hotbar to use them like the Magic Mirror (raise arm with item in hand):

1. Molten armor: costs 40 mana, grants the Inferno Potion buff for the current room.
   
2. SanTank-mini: costs 90 mana, grants the SanTank mount for the current room.
   
3. LongShot: costs 20 mana, grants a Double Hook for the current room.
   
4. Rocket Boots: costs 30 mana, grants a Rocket Boots for the current room.
   
5. 3D glasses: costs 50 mana, summons the Twins Minion for the current room.

You get the idea: implement potion buffs, mounts, minions and other stuff.

The active items suggestion is something I consider to be part of a 'major update' as a new main feature. But here's also some minor things I think could be dope:

• Extra rooms as Dead ends: To confuse the player and provide more 'mana charges' for the active items. This also would make more interesting using the map while going back to the start as to not get trapped.
  
• Bosses always dropping a red or active (golden) item: Sometimes the room before the boss gives me a good red one (like the crown) while the boss gives me a duplicate for a blue item... this feels weird.
  
• Enemies dropping coins: To buy items if needed inside the 'transmutation rooms' (dont know its correct name).
  
• Increasing damage by 10 after each boss: To feel some kind of 'progression' damage-wise and clear the enemies faster when going back. This may need to adjust slightly the bosses and enemies health or defense (if any).
  
• Eater of Worlds taking x2 damage on the head: I mean, why not? Or maybe a damage reduction of x0.75 if targeting the body.

This is only my opinion on how to improve an already amazingly made mod, would you change something?