Though I-banking is one of the top feeder industries into b-schools, your area of expertise (Compliance) is in a niche and unique domain. That gives you an advantage. You won't have too many people with your profile competing for those few coveted seats.
Your overall GMAT score is good. But considering the facts that you've shared (quant score, GPA, economics grade et al), you might get some raised eyebrows from the person reviewing the application if you submit it in the current form. Your plan of mitigating this with additional courses in statistics and calculus is good. Go ahead with it. If there a possibility of re-taking the GMAT to balance out the Q/V scores, that might help as well.
Due to the demands of certain professions, community involvement may not always be possible. However, it doesn't need to be X hrs/week kind of an involvement. You could do something that's not location specific. For this year's apps, you could highlight whatever you've done rather than try to force fit something at the last moment.
If you are seriously concerned on the EC/non-profit front (e.g. you get feedback from some of the schools), then you could take up something that has a more serious involvement. It won't looked contrived as you aren't showing something for 3 months just before sending in your application.
In terms of your work-ex, the size of the Asset Mgmt Firm doesn't directly say much about your scope of work. If there's a way for you to link your compliance work to those impressive looking numbers, it might have more impact. Right now it just tells the Adcom that you work for big companies. If your work has more than just an inward focus (internal processes, systems, regulatory controls etc), then highlight those aspects as well.
Your career aspirations do not seem impractical. You are looking for a new function within the same industry. That's not too much to ask for. In your essays, ensure that you explain your motivations well and link them with your strong understanding of the underlying processes.
Good luck with your applications.
Sameer Kamat | Founder - MBA Crystal Ball | Email: info at mbacrystalball dot com