Howdy, my name's Noel and I've just started writing custom careers for the sims. All of my careers are EP compatible and won't overwrite any other careers, they've all tested just fine.
If you have an idea for a custom career you want made, feel free to send me a private message. If you have SPECIFIC ideas (i.e. levels, wages, promotions, chance cards etc.) then include those too, it'll make it a lot quicker. Also, I'm not much of a graphic artist so you might want to think about doing the logo.