The 120 doesn't go that senior. The top few DEN captains are really senior and it is pretty junior after that. It is much more common for bro f/o's to upgrade into the beech. The reason 1. They bro only go's to three different places, and 2. Unless your super senior you would only be able to hold a ISN domicile. But in theory you could probably transition within 2 years w/ the company.