The Legion can and does represent some aspect of the Fallout theme, but Caesar never comes off believable. I just don't buy his stupid reasoning and I don't understand why he is at all feared by anybody. Because, first of all, he invites my character right into his fucking tent. Talk about a suspension of disbelief - the main baddy of the entire game asking you to come over almost as soon as the game starts? It's like asking for me to beat the game. It made me feel like he was stupid - how could he trust I wouldn't just pull the pin on a grenade and kill us all? Or I don't know, fuck him over in any number of possible ways.
His "stupid" reasoning behind what? Uniting the tribes? Conquering the mojave? It's the same as every other shithole nation in Fallout, Caesar wants to bring civilization to the waste, -begin again- , a civilization that can survive, and even, thrive, in the wasteland. I really don't understand what's so difficulty to grasp, care to give something specific. He invites you in because he isn't afraid of you, he takes your weapons before you enter, and you're surrounded by armed guards, and caesar himself is a miniboss in toughness and skill. Game mechanics aside, you shouldn't be able to beat him easily. Even then, it changes absolutely nothing other than an ending slide, as Lanius is already set to take over. (I'll admit that giving you the chip without having any way of ensuring you destroy the bunker was idiotic, I can't justify that shit writing..)
I can accept giant scorpions because the hows and whys of their existence is simple: radiation. It's like magic - it is magic. Caesar is human. Caesar is not magic. There's no supernatural force behind his rise to power, he apparently is winning because the NCR doesn't know how to fight crazy tribals - how thematic and inspiring. Caesar is a human with a dumb idea that I can't refute in-game because I'm never given the right dialogue options. So, since I can't convince him of his own stupidity or even argue with the man on any meaningful level, I reject him and kill him. It's as simple as that. Him and his army are meaningless to me - I'm playing a video game, I do a few quick-loads, get my stupid mini-nuke ready, and whamo, he's no more. A robo-scorpion is also different in this way - there are only so many mini-nukes and OWB is quite happy to ensure there is a steady supply of robotic terrors everywhere, so they actually end up being an actual menace if you play that DLC at a low enough level. I never feared the Legion, but goddamn, did I hate those sniper scorps.
His rise to power is thoroughly explained, pay attention. I don't know what more you want, he was smart, cunning, brutal, ambitious and well educated. He taught the tribes how to fight, maintain weaponry, use tactics, and to be brutal as fuck. Yeah so, the NCR, being a tribal village in Shady sands that tries hard to LARP pre war America being unable to beat a massive army of armed tribals and raiders that are better trained, stronger, and more dedicated than any of the dregs in the NCR, is apparently unbelievable.(Remember, the NCR isn't the modern government, they're not even the remnants of it. This isn't al Qaeda vs modern America, it's two large warring tribes that LARP different dead nations. ) Besides that, this isn't the whole NCR, the NCR is not unified, they don't all want the same thing. The NCR could surely crush the legion if they mobilized their entire army, enforced a draft and just ran them through, but they can't, because of the very inadequacies that Caesar removed from his legion.
I would have rather seen Motor-Runner replace Caesar - at least the Fiends have that whole hedonism thing as an appeal. A game centered around the NCR and the Fiends could have been way more interesting. It would have been much easier to humanize that group as well, to make their cause attractive. Sure, the Fiends rape and murder almost as much as Caesar's Legion does, but they don't do it under any false pretenses; they're the personification of wild chaotic abandon, human desire unbound. Psychotic hippies with a lust for power, drugs, and sticking it to the NCR. In a way, they're more deeply connected with the wasteland than Caesar's stupid attempts at emulating ancient humans. At no point do you even scratch your heads at who, what or why the Fiends are.
Emulating ancient humans? lolol, like the khans, kings, NCR, brotherhood, etc etc etc.. So, fiends are appealing because they are hedonistic, and Caesar is bad because they ban wasteful behaviour? Your ideas sound boring, your game sounds awful, NCR vs fiends, lame. The NCR already has junkies, that's why what you're saying is boring, the NCR is free, the NCR is wasteful, weak, divided. The Legion is efficient, strong, cruel, and strict, these are good contrasts. The legions is a far right nation, that not appealing to you doesn't make it bad. Hedonism is as connected to the wasteland as overeating is to africa, how can someone indulge in excess in a world of scarcity and limited resources?
Also, the roboscorpion bit is wrong as well, The legion assassins attack after Caesar's death, and the war at the dam is unchanged. They don't cease to be a threat because you killed Caesar.