You have strong points there. But don't you think Stony Brook wants to compete with the other National Universities. The profile of Stony Brook is "a National University oriented in research and graduate work, member of the AAU, but still considerably behind its peers in Athletics".
The question would be whether Stony Brook is looking to follow other peer institutions or would it head in its own direction away from other AAU institutions that offer athletic programs at the highest level. Regarding the Ivy league schools, they are a big-time exception. The "elite" status of Ivy league school allows them to stay at the FCS level and still get mass publicity from other areas besides their athletics. Stony Brook is not an Ivy, and it will never be.
Other peers institution in academics would be Buffalo, UConn, UMass, Penn State, Albany, Ohio State, Wisconsin, Indiana, Virginia Tech, Virginia, etc. These are all schools that are oriented in research and have a "flagship" status as state universities but with the exception of SUNY Albany all of them offer Athletics, specifically football, at the highest level.
In my opinion, this is the way to go if you are a National University outside of the "Ivy League" and other schools like NYU, MIT, Carnegie Mellon, John Hopkins that do not offer Division I athletics at all.
The infrastructure issues that you point out are important to address, but as always, they can be solved with the expansion of Circle Road and the North, Main, and South Entrances to Nicolls Road. Of course, the three villages have to be taken into consideration and traffic must be directed in such a way that minimally alters the current traffic patterns of the adjacent towns. While the relation between the University and the towns are not the best, in some periods of time even hostile, I'm sure this can be addressed in the best way possible. Traffic would only be a problem if things are not done properly. The current state of CR-97 (Nicolls Road) is more than enough to handle 20-60k people attending a football game on a Saturday afternoon.
Considering we have a large commuter student population that comes in everyday, this wouldn't be much different from the current traffic patterns.
From reading the above, its obvious I support a move up to FBS, I see it as our destiny even though I'm sure many would disagree. I visualize Stony Brook competing for championships with the top universities of the US, fostering regional rivalries with UConn, UMass, Buffalo, Temple, etc (in football that is)