Well all three factions are in it for control of the region. It's not like they're aiming to let the other waltz over them and be okay with it. Also Yes-man isn't part of it if you don't go along with him.
For the most the ending is NCR vs Legion, with a potential of House/Independent vs Legion.
What? I don't recall that being done. I never was playing nice with the legion, so that might be it. Otherwise there's no outright hostility towards you.
So a stalemate is possible without the player but with one impossible.
This is not in the spoilers so I'm limited in scope of details.
Just believe me when I say it's possible to end the game with a faction rep of adored by all factions.
It's possible to help or not hurt greatly every faction in game, at the same time without conflicts, or active involvment.
What is impossible due to the MacGuffin is that it's 100% ineffective as you're pigeon holed into one ending.
With no thought beyond it has to be a big finale finish, lets have bangs and combat.
Using as you say the endings you only have 3, for yes man / house is a carbon, clone, doploeganger, cut out copy of each other.
NCR, which is almost exactly the same as House / Yes man.
CL different slightly more but still the exact same resolution.
All these are just an illusion of choice, all those you made in game, all the thought you put in.
Is worth nada, it is the water purifier FO3 again just not as obvious the first run through.
There is no smart ending..
The dialogue choice?, you had that in FO3 too.
That did not make it any more of an option, speech check one line or kill, after a linear fight.
NV three speech checks or kill, after a shorter linear fight.