Natural Gestalt

[Manethereon]

My group (mainly one person in particular in it) really want to multi-class but not at that deficit that comes with that, spreading butter too thin. I gave them the option that perhaps there is a way in the game world to achieve two simultaneous levels (a gestalt level) for x amount of time, but that each consecutive one would be more difficult in some way than the first.
And this power could come from an artifact, a powerful magic user, an experience (traumatic or otherwise) the characters go through or an extraplanar / divine or infernal experience.

I was thinking about making it a mix between hard choices and hard encounters - splitting up difficult threats with difficult opportunities.

For example, a demon (classic) says he can grant them the power they seek, but they must do something heinous in return. This affects their character's alignments, and their abilities to return to some of their other quests but they are granted the powers they seek.

What are some cool other ways to involve a gestalt class naturally into the game world? Cool ways to make them more difficult beyond the first to a near impossible amount after x levels?

[Cyrocloud2]

I think this can work for gestalt. I had the idea for a mythic campaign that my PCs would have to go through a operation from a Kyton to ascend to mythic status, but they could only gain Mythic points by consuming Mythic creatures. These points would not replenish naturally. They would also then gain any specific weakness(Vulnerability to fire, or vulnerability to anything that would normally bypass the creatures DR) the creature had, the PCs would also detect as the same alignment as the creature. This would both allow me a certain control over their power and leave them in some tough situations where they may have too maim or kill neutral or good creatures so that they could combat a greater evil, and maybe even cannibalizing their fallen brothers in arms to preserve the mythic points. Hell I even contemplated through a mythic troll at them, so they would have a continuous supply of mythic power, if they kept it fed and it didn't go on a hunger strike.

This idea could be used for introducing gestalt in the way that they would gain class levels of those they ate up too their HD, how permanent or temporary this would be would be up too you. Maybe make leveling up the other side something like each level they would have too consume somewhere between 2 and 3 of the class for 1 level on the gestalt side in that class. So eating 2 level 1 fighters or 1 level 2 fighter would gain you 1 level of fighter on the gestalt side.

Then raise the amount to grow to the next level by how ever many class levels you decide as the standard to the next level. Example if you chose 2 levels of fighter to be the amount needed for 1st level then to have 2 levels of fighter you must consume 4 levels of fighter, 8 for 3 levels, 16 for 4 levels.

Sorry if I'm having trouble stating the idea well but the equation would be Y=A^n, with Y being the amount of class levels that must consumed, A the amount of levels that must be consumed, and n is the gestalt class level.

This would lead too you PCs hunting down murdering and eating NPCs to fill out their Gestalt levels. Hell to get to level 20 they might have to eat 1.05 million class levels.