Based on my opinion, I think working people who wanna study part time would most likely want to expand their knowledge rather than looking at the qualification of the paper especially if taking a part time degree course.

If its all about the paper and better opportunity, might as well work full time until you are good enough to enroll for MBA.

Getting a Degree from an open uni won't hurt your career much when you have the experience. It will help you to gain a positive image when you're in an interview.