I'm still getting out of the starting gate on the game and have recently remade a new character to try out a different build, since my other one was too spread out.

So far, I've enjoying doing a lot of the sidequests for the towns outside of the strip, but I've gotta know before I go and waste 100+ hours of my life: If I get further into the game and side with Legion, is everyone and their mother going to auto-hate me, including towns I've already reached at least a "Liked" status with? Or should I just say screw it and murder everyone and skip quests because that's what the game expects me to do if I go Legion?

I ask because I'm reading a lot of the threads here that make it pretty clear that the game was designed to be extremely bias, play-wise, in favor of the NCR.

I've also read that if you wipe out NCR areas, the Legion would move in. Does this mean that I could slowly "reshape" the map to be Legion-dominant, without trashing all the side-quests?

No matter which faction you pick, you're gonna get shafted with a bunch of others. Example: if you choose NCR or Caesars legion, you can't be friends with BOS (well you can temporarily, but not long term). And there are a few small contention camps where you can aid one faction gain advantage over the other thereby subjugating the real estate, but those instances are few.

You CAN be friends with BoS if you join NCR and even seal a truce, though hilariously, you still lose a tiny bit of NCR rep and the commander complains about your 'success'.

Yea, I expect that there will be some opportunities gained and lost through faction siding.

My main concern is whether or not I'll be blowing away the vast majority of them by ticking off the NCR. I did this once already when I sided with the Powder Gangers and found I couldn't even get past Nipton without Rangers swooping down on me, and I had JUST managed to finish the quest for Primm's new sheriff before my "three days" were up -- since two of your three options REQUIRE you to enter the Mohave outpost. Had I waited too long, the quest would have been undoable until my science skill was quite high, and there's no telling of whether or not I would have even been able to get back INTO Primm with the NCR camp right on top of it.

There's an NCR guy in Novac, as well, and something tells me if he went homocidally crazy on me, the rest of the town would have, too. And it just seems to me that this is going to be the pattern.