Math/Econ or Business Economics

Yes doing well in Business Economics and the Accounting minor will give you pretty good opportunities in i-banking especially on the West Coast

IT DOES NOT MATTER

I am in a similar situation at a nontarget, and I am taking the math courses, they show you are willing to study for long hours and have at least a baseline intelligence, something IBs are always looking for.

Minoring in accounting would be very helpful for the reason you've stated. As for whether you should go math/econ or business econ, it really doesn't matter. Though if you go math/econ, it might be more fulfilling since business econ is "softer" than normal econ. Also, should you decide to go to grad school in the future, math/econ will set you up nicely.

If you can do well in the math courses, take them as it will only help. However realize that the latter combo plus the accounting will set you up better for IBD.

Go, Econ/Math or quantitative economics and mathematics with a minor in ACCT. If you F$^K up in i-banking for some reason or get bored and don't like i-banking you can always lateral to the FED or the Treasury Department or some other i-banking interactive government agency. Insurance underwriting (actuarial and accounting mathematics) as well has a i-banking aspect.