There is a "best before" date for banker/PE types.
You'll find that the overwhelming majority of banker/PE types have around 3-4 years experience, with the outliers having 2 or 5 years on each end. This is a function of the applicant pool itself (most banker/PE types apply during this time), but also what adcoms expect because the career progression is so structured and regimented.
You're in a catch-22 situation. If you are already a few years into a post-MBA role, you'll have a very tough time convincing the adcom why you need an MBA other than for a trophy (since you're staying in finance short-term and not making a drastic career change). If you are still in a pre-MBA role, then the adcom will question your ability/career progress since most banker/PE types with 7 years experience in finance are already knee deep in a post-MBA level of responsibility.
Put it this way. You can't window dress in 3-5 months to fundamentally change how they see your overall body of work to date, starting with your 4 years of college and your 7 years of work experience. Big change takes time. You can't just all of a sudden crank up your extracurriculars and hope that it will make that much difference (because like anything, you need to put in the time for ANYTHING to be in a position to succeed - not just in your career but in anything that you do).
From a practical standpoint, all you can and should do is to wait for the applications to come out and do the best you can on them. With your profile my hunch is that your chances are slim to none at HBS, Stanford and Wharton. There's a lot of banker/PE types, and they would rather take the younger guy with less experience.
In your case, it isn't a question of caliber -- it's a question of timing. Which is something that an adcom will have a hard time overlooking. If you get in, consider yourself lucky and blessed. But if you don't, don't be surprised at all.
Here's another way to put it. If you feel that an MBA is really worth your while from a substantive standpoint beyond just "brand" (i.e. you really want to change careers and get out of finance, you want/need a break and you're burnt out, etc), you would probably be applying to a broader range of schools and would probably be genuinely interested in going to a broader range of schools. If you're just focused on H/S/W, you may not have strong enough reasons to go beyond the "trophy", which may be hard to admit. Branding only takes you so far once you've developed a body of work in the real world -- it matters for the less experienced and the really young, but at your stage in your career (if you've truly been in a post-MBA position for a few years) it's a nice dessert, and not the main course. The thing is, are you willing to pay a fortune just for a dessert? Especially when you already have a business education in the first place.
This may be hard to hear if you've put so much thought and attention to your MBA plans, but I hope you take what I say in the spirit of constructive feedback.