Pulling a signed offer in attempt to shift into a different position within the company?

Hey all. At the end of my internship, I accepted a return offer for an institutional asset management position within a bank. However, I realized I always wanted to work on a trading desk and this company has an FX and FI desk in their capital markets team. Their applications for their capital markets program are still open, however I'm 4 months away from onboarding and start at the end of summer. 

Would it be risky to voice it out to the recruiter if it's possible to interview for the capital markets team and see if I could make the switch? This would all be at the same company so I'm not sure if there's any risk. But I also guess I could get a year of experience under a portfolio manager (which is part of this rotational program) and try to make the internal shift after.

Nonetheless, I don't see a future for myself in AM and would really like to switch onto a trading desk, but I reckon it would be a great resume boost to have AM on the resume.