As an American raised Saints fan I think this is a great idea. My one worry is that the team will need the commitment to stick it out as it will likely take at least a decade before a significant return on investment is achieved. However as others have said there is an incredible amount of potential, both in terms of potential players and fans.
To address some of the comments above, there I agree that there is an incredible amount of raw athletic potential in the states. While one would expect this would correlate to more successful footballers, the reality is that the current system is weighted against producing them. Despite a decent of young Americans (ages 5-13) playing organized "soccer" this is almost exclusively on recreational teams with minimal commitment levels (a few months a year, poorly coached, lots of turnover, etc). Many of the most talented athletes from this pool abandon soccer once they attend high school (age 13+, the US equivalent of secondary school) to focus year-round on the big 3 sports (American Football, Basketball, and Baseball) in the hopes that high performance will attract university recruiters and scholarship offers. Then, once at university, the goal is to attract professional recruiters and land on a professional team.
Therefore most of the soccer players remaining in the US who look to play professionally are those who simply love the game and continue to take whatever opportunities they have to play it. Unfortunately, because of the shoddy coaching and team structure outlined above, these players are quite often not very talented athletically (those are generally claimed by other sports) and/or technically (because they've been poorly developed). Contrast this with the women's side, who, without the competing rivalries of established professional football and baseball have seen much more robust development programs, much more support at the university level, and a much more competitive team on the international level.
Second the tide is currently growing against allowing participation in football at the high school and university level. It is possible that in a few years' time the game will be deemed 'unsafe' to be played in schools, which would completely shift the development landscape. This, combined with a general growing interest in soccer due to historically better performance by the US national team, a surplus of funding $$$ injected into MLS, and growing media coverage of international soccer, means that a portion of prospective athletes could be persuaded to see professional soccer as a viable career path and join something like an academy program.
Finally all these same reasons mean that there are many folks becoming interested in the PL. Most newcomers go to teams that they've heard of (the big 4). Anything to get Southampton on the map would be an increase as the majority of casual soccer fans here have never even heard of the team!