How will an online MBA be perceived in applications for a faculty position in economics and accounting?
It will take you out of consideration for any faculty appointment. MBAs are headed to industry; to teach (be hired on tenure track), you need a relevant Ph.D. This doesn't depend on whether your program is online or not. 

Come to think of it, depending on how interesting and high-level your prior job was, and if teaching (as opposed to research) interests you, you could target an adjunct position instead.