If I was really there then I would side with Mr.House if I was on the Strip, or the NCR if I was anywhere... Hate to say this, but propaganda just works on me in real life... yah I know its bad.
From a third person perspective watching this like a movie/book then any faction would have to majorly change for me to back it.
However I know I am sticking my rear in the fire I think the Legion needs less change then the others.
Changes the Legion would need.
1. Kill off Ceasar. He is a hypocrite who should have been seen as week ages ago, and killed by his fellows so a stronger leader could take over.
2. Kill off Lanius. While he follows Mars, and seems to have the Legions best intrest in mind he has little care for his fellow soldiers.
3. The best chance for the Legion to actually stand as anything the current Ceasar thinks it should, it would take a natrual born, and raised kid to rise to the top.
Why do I think the Legion is the best option for the Fallout Universe?
The best way in my book for 'ALL' of America to be united under one banner is through an aggressive, and oppressive reign. Yes the Legion are harsh, horrid, and brutal, but guess what? So is the wastes.
Now do I see the Legion being the barbaric policical org. that takes over all of America? Sadly no.
As I said their leader is a hypocrite, and there second in command is a lunatic. It would not take many high ranking deaths in the Legion for it to fold, and revert back to little tribes. And finally there distrust of Tech. If the Legion started moving East they would eventually run into the Midwest branch of the BoS, and there robot army...
Robot army vs Legion swords/guns == curb stomped Legion
As it stands though the only two political groups that could unite America from sea to sea is either the Legion, or the Enclave (when it was at its prime), but we all know how the Enclave is now standing
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