>find a worthy successor
May not be immediately necessary, he could have plenty of time even if it's none of the listed choices or the Courier, since we have no information on how long a cured Caesar lives after the battle.
>Yet in the ending where he becomes the new ruler he annihilates almost every faction and settlement without even considering the potential advantages of having them under their rule (something Caesar does). To him the Legion is nothing but a mean to keep engaging in his path of war, and is his refusal to forgive anyone in the end what convinces me the most that he'll eventually get the Legion destroyed.
I don't think he's as capable a leader as Caesar and he's definitely more warlike but the fact he can have pause at all is notable, I would sooner have Lucius or the Courier or Vulpes in charge though.
>Considering that the game ends stating that the player continues to drift through the Mojave
It does not say this. It says the wasteland is forever changed and leaves it open, nothing about you continuing to drift. In some endings it implies you stick around like House keeping you at the Lucky 38 and if you had good karma, "with pride in his choice of lieutenant."
Or "partly out of fear" with bad karma, but nonetheless - sticking around at least in the short term. The Legion doesn't specify, but it doesn't say you keep drifting either.
>It's stated multiple times in the game that the NCR army is weak in New Vegas because the best rangers are guarding New California and the ones sent to Mojave aren't enough to cover the whole territory. A war in its own territory would be much more different than the one shown in the game, since the NCR would start with a strategic advantage.
That's what I'm saying though, they aren't going to lose the Mojave in a disaster and then immediately head straight back in, Caesar would have a lot of time and territory on his hands before he even had to think of the NCR again especially with the likely ensuing chaos back home from their being humiliated.
>That's the thing, in a Legion victory over the Mojave the NCR would be forced to fight them again since the Legion has an expansionist politic that eventually will put the other states of the republic in their eyes.
In the long term I think they would go to California and try to conquer and incorporate that as well, but Caesar's whole purpose with New Vegas is cementing his wandering army into a more settled empire. Though I will grant if that delays more advancing into NCR territory they would also have time to regroup themselves as well, and taking NCR itself would be a challenge for sure. I just don't think if he has New Vegas and the NCR has pulled out after losing they'd be right back there attacking Caesar in New Vegas. I could see them harassing or scouting out the Legion routinely though.
Another element we aren't considering is Lonesome Road by the way, while not an ending slide element, if you nuke NCR in that DLC their ability to interact with the Mojave at all is pretty fucked up I'd imagine, and probably a good bit of their territory at home. I will grant this is speculation, but they are nukes launched at NCR and the Long 15 and all.