If you want the best turn around I would suggest getting another NE axanthic. These snakes are highly regarded and are good sellers. You might have to do some work, but adults do occasionally become available. Start asking around now.
There are some that like subspecific crosses (brooks x getula), and some don't. There has not been an axanthic bred to a eastern as far as I know. So from that perspective you might have some curious people interested, but might be more work trying to sell.
There are some very nice subspecific crosses, particularly the axanthic brooksi x goini Brandon Osborne has produced. who knows what an axanthic brooks x getula would look like in two generations... I have always wondered if some eastern populations are a natural axanthic? I guess it comes down to whether you want to play it safe or be an experimenter. have fun, be honest with your customers and you will be OK.
daveb