This is EXACTLY THE ANTITHESIS of what my pre-med advisor told me (early on in my post-bacc). His words were, more or less, "Off the top of my head, I cannot think of a student who has gotten into medical school who did not apply early in the summer. My experience has been that students who apply in the fall almost always end up as reapplicants the next year." He happens to also be on the faculty of a top med school, so while I think what he said might be a bit of an exaggeration, I think it also says something about admissions -- long-time SDNers who say "apply ASAP -- as early as possible in the summer ~18 mos before the intended matriculation date" have a lot of evidence behind what they are saying. Med schools are using rolling admissions after all.
OP, if you do not score above the avg of the schools to which you are applying (taking GPA into consideration) and are unable to submit your primary (w/ the MCAT) prior to Aug., I'd probably suggest waiting a year and making sure everything is in place long before you hope to apply. Being a reapplicant will only make things tougher the following yr and you will be a reapplicant at all schools if your primary is verified by AMCAS. It is irrelevant whether you withdrew an app later or only applied to one school and then withdrew the next day. You are still a reapplicant. (Although, I suppose if you withdrew the next day, they probably would not have started the verification process so a call into AMCAS to have them cancel it MIGHT prevent you from being a reapplicant but that's getting a bit complicated....)