Agree with Anderson. Until there is enough support in Phoenix, there is no stop in Phoenix, which makes part of that plan very hard. On the east end, Dallas to Houston to New Orleans seems like the correct daily train to me. Stop at College Station...
Phoenix is a bit of an odd duck:
Another thing to consider regarding Phoenix is that its status as a major airline hub is likely to change over the next decade. When USAir merged with American Airlines, one of the conditions of Justice Department approval of the merger was that the combined company would not make major reductions of flights at any hub for three years after the merger. One of the big reasons for the imposition of this restriction was that it was pretty obvious to everyone in the aviation world that the new AA can't sustain major hubs at both LAX and PHX: they are too close together. So it is pretty obvious that as soon as the three year window expires, which I believe it this coming December, AA will start more or less drastically ramping down operations at PHX, since obviously they can't reduce their international and transcontinental operations at LAX. Since the merger, they have been slowly increasing their domestic operations at LAX and making significant capacity improvements at LAX.
So, the long and short of it is that there is a real possibility, at least, that PHX will become much less convenient to reach by air over the next decade, which will change the cost-benefit analysis of improving Amtrak service there.
Ainamkartma