Hey Andy, sorry for my late reply. Depends on which bank you are aiming, GPA requirements may apply esp for larger banks eg HSBC, which is 3.2 / 4.0 at least. For other banks, actually it's more important to have relavant internship experience eg Bank intern / co-op / placement in CMB will be great. 

Checking from LinkedIn, I can tell most of those who are now GTs in CMB are graduates from business majors. But I don't think it's a matter indeed, it's more about whether or not you have accumulated some relevant experience in seniors years.

We didn't keep an eye too much on the exit opportunities for CMB GTs if one is going to quit from banks. But I personally know a friend who was a RM from a multinational bank and changed his job to be a RM for an prestigious international auction house. I guess more or less you will still be working in client management roles.