So, I am doing new playtrough, my last, noobish one was side by side with NCR, Followers, BoS and Great Khans, I killed every Legion guy I met, not because of me, but because of Boone, he is great at all, but his hatred towards Legion made me think that Legion guys are hostile by default, like raiders, Arcade also hates Legion, so does Veronica.

I want to be idolized by Legion by making all quests and then betray them, but will the fact that I am idolized by Legion ruin my companion situation, I know that both ED-E and robodog will never leave me, but I love Boone and Arcade, and I don't want to loose them.

Will they leave me forever if I try to side with Legion?

Arcade will leave you around the "no turning back" point, when you've done enough quests for the Legion that the NCR path is closed to you. I think Boone will as well, but nobody else. They'll both give you a warning beforehand as well.

Boone most definitely will, he wants nothing to do with the Legion. Same with Veronica though she's not quite as intense about them. I'm not sure about Arcade, I've never played with him. That's one of the consequences of the choices you make in the game, sometimes you have to settle for a sacrifice. One companion that won't be upset is Raul, and I'm not sure about Lily. She might be good with that arrangement, I just don't know where her loyalties lay. I've never played with her either.