have you thought about taking a gap year, if you are certain that by next fall, you will get your citizenship?
Consider the following:
(1) It looks like you are aware that even the merit awards are really NOT blind to nationality. For international student (and you are an international student as long as they are concerned since you don't have a citizenship), this is an issue. In many (perhaps even most) schools, merit scholarships are mostly a tool for them to recruit top students who otherwise might not choose them - in short, the money is an incentive to lure you. As such, the odds of getting merit scholarship ONCE you are already a student is much, much lower than getting a scholarship as a freshman applicant. Hence, you shouldn't assume that you can start your freshman year as a non-citizen without merit award, and get a merit scholarship once you become a citizen.
(2) The need based financial aid that will help you in case of less than 4 year national scholarship is also contingent upon the citizen status. Many (even most) schools that go on and on about how they are meeting full financial needs and their admissions policies are need blind will have a caveat/fine print that excludes international students (anybody without a citizenship, regardless of whether you have a green card or not).
(3) Campus ROTC scholarship is NEVER a sure thing. If you decide to go to a school, and if you don't get a scholarship, what are you going to do? Can you afford the pay for the full 4 years in whatever school you go to?
(4) the more I learn about this whole thing, I am starting to think the ROTC scholarship (at least in Army) is much more than money. It gives you the "contracted" status as soon as possible, and there are some highly sought after summer programs and additional training opportunities and what not that are not available to ROTC cadets who are not contracted.
If you get a 3 year AD scholarship, you won't be contracted until the beginning of your sophomore year, and whatever sought after training opportunities during the summer after the freshman year is not available to you. If you don't get a campus scholarship, and become a non-scholarship ROTC cadet, I believe the earliest time for contract is the beginning of the junior year, at which point, you already missed out on highly sought after training programs his/her cohorts were able to benefit from. This, in turn, disadvantage you in the branch selection OML.
In the big scheme of things, one year spent as a gap year is a very, very short detour and delay, and especially, if you explain this in the ROTC scholarship application next fall (meaning, you took a gap year to become a citizen and then apply for the ROTC scholarship), I would think they will have absolutely no problem with that - if anything, that would make you look really focused and committed, I would think.
It's a non-linear option, but think about it.
CAVEAT: my opinion on (4) is based on discussions and anecdotal feedback my son got from various PMSs, ROO, etc. I never heard this as an official policy. So, anybody who can contradict me with fact based data, please do so.
So I plan on pursuing ROTC and apply for college-based scholarships once I hit college. 
