Other base lists can be very powerful; that's another reason why we dont allow them to be chosen as base lists outside their profession. Generally speaking, base lists are the most powerful lists in the game, followed by closed and then open.
One other thing to consider is that, IIRC, characters are only supposed to have six base lists total (I dont have the rules with me so there might be various options and an option to have up to 10?l). But i think one should keep a maximum number of lists total, again for balance reasons.