I thought of a new NPC that could fit in the game nicely. This time we could maybe find a Lady that lets us collect Health Pickups into HP Flasks with max charges and activated with a hotkey.
Most of the time my HP Pickups get wasted, as they always appear when my HP is full or almost full (just my luck), I believe this would be a nice addition with lots of room to further develop this mechanic through upgrades.
If you ever add collectible materials other than Gold, they could be used to upgrade the potions (or just use gold for normal upgrades). The ability to increase max charges upon each first final boss kill of each stage/map would feel very rewarding.