Well, people definitely do it, but it is rarely looked upon as a good idea. For the most part, the CONS to doing it is that it really serves no great purpose, and only pollutes the lineage of TRUE locality animals. I am not a huge locality buff, but I can see their side of it. When you think about it, why would you want to breed a suriname to a peruvian or a colombian to a guyana? If you like the characteristics of one locality, simply pair it up with an animal of the same locality. It's not "cheaper" to do it either since a pair of common boas is generally less than the price of one common boa and one suriname for example. The resulting offspring generally demand deflated prices since you basically have what many consider to be "mutts". In many cases the resulting offspring would simply be considered intergrades, but you'll have a hard time finding people that buy into that reasoning as well. There have been MANY arguements on this forum regarding the practice of breeding locality boas with morphs such as albinos for the sake of profit. In the long run, you can do whatever you choose as you know, but it will more than likely come under scrutiny from many keepers if you choose to cross boas. As for the PROS of mixing surinames with colombians, for example, I can't honestly think of any PROS to doing it. Well, I hope this didn't come off as a lecture or rude, as I didn't mean for it to be either. Best of luck with your new boa, and your future breeding ventures. Take care!
Paul