Hello all,
I'm an old experienced Fallout player, but I never did the Legion ending before.
Too unpleasant...
But I figured, I need to check it out! So I revved up my full BadGuy mode...

It was IMO not so good.
They never do let you join the Legion. They continue to call you 'vistor' and take all your weapons - right up to the end of the game!
No side quests; no Legion Armor or equipment; no Legion lifestyle...
No Legion, basically.

I was pretty surprised, heheh... I mean, I destroyed the BoS for this!?
The only good thing was venturing beyond the UltraLuxe and into the NCR Embassy part of the Strip.
The NCR guys went crazy, attacking me (with their Cattle Prods) heheh...
Which caused every Securitron on the Strip to go hostile.

So I killed every NCR and Securitron - in self defence of course.
Now THAT was entertaining...

Hey maybe I can do Mr. House now too, since the only thing putting me off was the BoS thing.
It's pretty bad how the Devs steer you into BoS membership, making 1/2 of the four endings... unpalatable.
I'll bet you 9/10 guys do either the NCR or YesMan ending.
Or what?

My current character turned on the Securitrons in the bunker, then sneak-killed all of the Legion in the camp, except the ones in Caesar's tent.

Since then they have let me come and go without demanding my weapons.

Hardly a pro-Legion character though.

Also I haven't really felt steered into joining the BOS. Maybe with Veronica as a sidekick, but even with her things can happen that can sour you on the BOS.

My main reason to join them would be to get power armor training, but of course there is another way to get that.