I have to say BOAS! LoL...

My 2nd snake was a BCI (columbian hypo female) and I got her for some of the same reasons you are concerned with. I could not be more pleased with her. She was only 2 months old when we got her and its so neat watching her grow. She pounds her mice every time, even when in shed. And she is so happy to come out and just hang out with me. She's even more mellow than my BP.

BP's stress when being handled. Even if they are generally cool with things and nicely tame, they still stress to a certain extent because, as a general rule, they are shy snakes. Boas are not shy. My boa doesn't stress in the slightest with handling. These snakes actually enjoy it.

And my baby is now only 6 months old and she's as mellow as a cream puff. Some do settle down more with age, but most will settle quickly once they get to know you and your habits.

They do get big, obviously, and maybe that would rule them out for you. But if you're willing to consider the steps you'll have to take to manage a snake that size, you won't be sorry. If size is an issue, hog islands are a great choice and a Dumeril would be a good option too (I don't have personal experience with Dum's but I have heard they've great personalities and appetites too - I want one eventually).