The title pretty much summarizes the problem.
A game problem is 'cursed' where there are 2 different mechanics that go against each other.
Cursed problems are by definition unsolvable. UNLESS...
Unless a compromise is made to accomodate the problems in a non-harmful way. But something must be given up to mitigate the problem.
Warframe is a looter-shooter game, what makes the player come back to the game is the constant stream of new stuff, mostly warframes and weapons.
Exalted weapons are anathema to this model, because they are embedded as a Warframe's power.
The looter-shooter model requires some level of power creep, gentle as it may be, as a way to lure players back into the game, otherwise there is no point in hunting new weapons.
But if a Warframe's Exalted weapon is the best in its class, why hunt for any other?
But if there are weapons objectively better than the Exalted one, why bother with having an Exalted weapon in the first place?
You see, those go against each other, in a cursed way.
Currently, Warframe is falling squarely in the second bold question. Exalted weapons, especially melee, are blocked from using several mods. Their stats and mod points falling behind (with Kuva weaponns going up to level 40). They are more or less pointless, and becoming more pointless.
This requires not only balancing, but some sort of compromise to dispel the curse.
So, I have been thinking of what I could suggest. I DO NOT CLAIM ANY OF THESE IDEAS ARE GOOD. They are just ideas. Feedback is welcome.
Option 1: spin them all off as Prime weapons, or a new class of equippable weapons, called 'Exalted' obviously. They would not have a button to cast, as they would be a weapon, but could have the associated energy cost, or a reduced one, and spend ammo, or just drain ammo over time in lieu of energy, or whatever.
Problems: New abilities for slot 4 would have to be created for every frame. Every Exalted ability would have to be reworked.
Advantages: New Exalted weapons could be designed and switched around. Frames could be limited to a small number of weapon classes, so not every frame can use every weapon, or just set them all free.
Option 2: Turn the exalted weapon in just a buff ability that affects the weapons in hand to use a specific stance (if melee), and have additional effects.
Problems: Abilities may become washed-out, generic, and less interesting. Potential loss of fun-factor.
Advantages: Opens up variety of weapons equipped.
Option 3: Exalted weapons become living weapons, that get stronger with every weapon of the same class that the player masters. (Every bow mastered gives a stat buff to Ivara's Bow, etc.)
Problems: The anti-MR-related-mechanics brigade with come with torches and pitchforks. Takes a long time to max-out an Exalted weapon. Every time a new weapon pops up, raises the ceiling for that class, increasing the pressure on power creep.
Advantages: Ties the looter-shooter loop with the Exalted Weapon, in a manner that even makes sense RPG-wise - the better you are within a class, the better you are with the Exalted weapon. Seems to be the one that requires the least effort to implement.
BONUS MECHANIC: Regardless of what happens with Exalted weapons, they should have not only Exilus slots, but also mods that act as sideways stat changes. Want to rebalance an Exalted Weapon's crit chance and status chance? There should be a family of Exilus mods for that - only for Exalted weapons though. They should have a secondary effect to better justify their existence though.