Was wondering if there's anything to stop people doing this..

On a main char take something like Cybertech, Scavenging and Underworld Trading. Then make an alt and take Slicing on that. The main sends credits to the alt for missions, and the alt just does Slicing over and over again until it's maxed out, sending all profits to the main.

Is this possible? Or is it like WoW where you need to reach a certain level to progress professions past a certain point?

It is possible, but you better unlock at least 2-3 companions with your alt, so they can all go out and do the slicing, othervise it will be a pretty slow process.

Btw. you need to be somewhat patient at crafting as well, since mailing isn't instand as far as i know.