why do you need to level him? you can just hit "kill target" think about this though... if you can level your toon, why pay for extra char slots through c store.
It's not a matter of "leveling the toon" ... that'd be more silly than trying to keep a "permanent" character on test.. It's more of a matter that if you are going to test the viability of a mission, it'd be nice to NOT use the Kill Target button, and see how an appropriately ranked character would fair in the mission you create.
I may be off base here, but to me, testing a mission isn't just about spelling all the text correctly, and formatting the grammar.. settting the "doors" to work between maps and whatnot. I've read FAR too many posts from the player base, complaining about missions that are too easy, or too hard. I just sort of assumed that with ranking up/down your Foundry toon, you'd have a better handle on figuring out just how difficult our missions are going to be when played by "real" characters.