ghost's fundamental problem is that she requires equipment to work. unfortunately, equipment is precious, hard to find at the right levels, and takes up precious scrolls of upgrade to make viable, so you and the ghost are effectively fighting for this very limited resource. instead, it'd make more sense for her to automatically scale (to an extent) as you progress through the dungeon like the other artifacts, and give her greater versatility in how you can equip her, allowing you to spec into a companion that matches your needs.
the rework itself:
the weapon and armor slots are exchanged for an offensive and defensive slot, respectively.
what you put in the offensive slot determines the ghost's behavior. options include:
-a weapon, and she will do the same thing she does currently
-a wand, in which case she will try to attack from afar and retreat when not firing (unless told to hold a position)
-stone of blast
-certain potions (liquid flame, toxic gas, paralytic gas, freeze, snap freeze, corrosion), which she will stay just out of range of and throw at enemies
-throwable items (missiles, explosives, spells), which will cause the same behavior as holding a wand
-scroll of retribution or psionic blast, which will not cause any automatic repositioning
what you put in the defensive slot determines how the ghost responds to threats. options include:
-armor, in which case ghost will take no special action to defend
-certain runestones (aggression, sleep, blink, flock, fear), which she will throw at enemies that get too close
-certain potions (invisibility, healing, earthen armor, haste), which she will drink when at low health and then either run away or stand her ground
-scroll of terror/dread
item scaling/recharge:
-weapons, wands, armor, and missile weapons act as if they have half the upgrades of the rose itself, rounding down (ex: a +6 rose with any scale armor equipped will act as if the ghost is wearing a +3 scale armor)
-wands can only store 1 charge, but recharge twice as fast as they normally would at that level
-runestones, potions, spells, explosives, and scrolls will not be consumed, but will instead gain a cooldown until ghost can use them again. in return, their effects are reduced for each individual use. cooldown and effect reduction scale with level
-missiles are still limited by their stack, but ghost will act as if you gave her 5x the stack you actually did (ex: giving ghost 3 fishing spears will result in her being able to throw 15). when thrown, the weapons will have a shimmery effect, and only ghost can pick them up, which she will attempt to do once out of combat (items thrown into a pit automatically return to her inventory). while in combat, ghost can throw a missile every 2 turns; if she runs out of missiles before the fight ends, she will tell you ("I'm out of missile weapons!"), and you can equip her with another offensive item. if you do so, she will return the other item after she picks up all the missiles ("Here's the [item name] back"). ghost will not decrease the durability of thrown items, and they have the same upgrade scaling as weapons and armor
i was also about to type out an idea for a button toggling her to prioritize staying alive or defending you but then i got tired and decided to just leave this blurb here instead