Is it possible to get the reputation with the Legion that is required without screwing up any game ending? (Like the main endings)
I'd like to get the lucky shades and the other things but I also don't wanna lose Boone or any other companion. After looting the safehouse I want to get a bad reputation with them again (vilified) And keep my new vegas strip, freeside, NCR reputation idolized (Or at least restore them)

Is that possible?

Pickpocket ~40x NCR dog tags and trade them to Decanus Severus for 10mm ammo (one tag at a time), after passing a 35 Barter skill check with Aurelius of Phoenix. That should get you "Liked", or very close so 1-2 harmless CL sidequests will put you over.

With all the generic NCR troopers in the game finding 40 to pickpocket shouldn't be hard.

-Gunny sorry, but I just had to.