I swear if Ulysses turns out to be the long lost Legion companion that I've been waiting on forever that I can take back with me to the Mojave, I will almost forgive Obsidian for how horribly biased the game is.
I wouldn't count on it.
The dialog in Honest Hearts seems to suggest that Ulysses was a Frumentarii whose job it was to obtain the Platinum chip. Instead, he deliberately dropped the job and basically betrayed the Legion, all for the sake of whatever grudge he holds against you. Other than that, the main game and the DLCs have just been so anti-Legion so far that it'd both be shocking if the VERY last DLC gave the Legion something and I doubt many players would still be on good enough terms with the Legion to use him. I mean, he could be pro-Legion in his opinions and who knows, maybe he is a companion, but I don't think his pro-Legionness would go any further than his opinion. A die-hard, pro-Legion personality would basically mean Ulysses would try to kill the NCR supporters, whereas the DLC makes it sound like he's willing to make peace with his hunt and be on his way/finally bring things to an end. Sounds more like an issue involving Speech to make him leave peacefully, not rep.
I remember reading somewhere that one of the Producers was in charge of two of the DLCs and the other was in charge of the other two. I
think the guy in charge of Honest Hearts is also in charge of Lonesome Road. If that's the case, don't hold your breath.
It's entirely possible. NCR would likely have no interest in that barren strip of desert even if it wasn't a storm-ridden go-here-and-don't-come-back place. Plus, it is just several miles west of where the Canyon wreckage is, and that has the Lonesome road graffiti on it.
The dialog also offers you to ask what he thinks of the Legion, Mr. House and the NCR. The Mr. House dialog is the usual "who the **** is that?" sort of response, to the Legion he basically says "no comment," and to the NCR he mentions some of the key problems they had at the First Battle of Hoover Dam. He mentions the Divide and the Big Empty being obstacles that the NCR has to work around when sending more supplies, with the Legion scouts and spies personally reporting that all NCR who enter the Divide are never heard from again. Big Empty is briefly mentioned as an obstacle but he stresses the danger of the Divide the most. Either way, geographically, this would put both the Divide and the Big Empty between Vegas and California/in California. Death Valley is kind of a big deal, so yeah. Come to think of it, I think he even confirms it's Death Valley, once calling it that.