Perfect - you answered it all in your question and well on the way.
I was going to say study accounting but you're already there.
I wouldn't "switch it" to IB / Finance just add another year to Accounting and make it a double with Finance.
As for Mandarin ? again good call I know a number of people that did Accounting / Finance / Law / International Business doubles with Mandarin elective over 3/4 years and now happily lost somewhere in Asia.
FWIW whatever you double just keep Accounting and add something to that.
