The biggest weakness is overthinking and overplanning -- it sounds like you're already planning your life 3+ years from now before even making that huge jump from college student to working professional.
Take it one step at a time. Do not underestimate the changes and obstacles you will experience in this transition - you will mature a lot, you will change your perspective, you will encounter things in your job/life that you won't expect. Do NOT take this for granted and assume "if I do X, Y and Z in the next few years and stick to my baked-in plan, I will be ready for b-school in 3 years!".
Again, don't worry about b-school. It may sound counter-intuitive because you've probably always heard that one needs to plan ahead, but in cases like yours (i.e. the personality types going into IB and consulting straight out of college) - it's usually the opposite -- you have to focus more on living in the moment and dealing with what is immediately in front of you, rather than trying to live three steps ahead (and getting neurotic about one's future and taking the present for granted - which can end up screwing you up more because you aren't as focused on the present).
Don't try and manufacture your resume for b-school - it's ass-backwards. If you're a compelling person, you're a compelling person - you will make choices that are best for your life, and your resume will be a byproduct of that, and not the reason for your career decisions.
The MBA isn't a magic slipper or some conditional gatekeeper that is preventing you from being some successful person (however you measure it).
Point is, focus on what is immediately ahead of you -- a very consuming job - and take it a step at a time. Because once you do that, you may achieve even more than you would've expected had you "lived" 3 steps ahead. Or you may not even go to b-school at all.
For a personality type like yourself (I'm being presumptuous, but given that you're going into banking, it's not a stretch to make that assumption), the greatest danger isn't lack of planning - but neurotically over-planning - turning your career, resume and life into some "plug and play" recipe.
A lot of things in your career and life WILL be non-linear -- rather than trying to force it into some linear progression, embrace the fact that it will be non-linear, random, and uncertain. You will discover something greater as a working adult than whatever you've tried to neurotically plan for as a college senior.
Again, congratulations on your job offer. Focus on getting through the first year as an analyst first.