I believe what Trevor is trying to say is that we feel you would be better off getting something else for your second snake. The jump from BP to Borneo short tail or blood is a big one. You say you will have the perfect set-up? So what you mean is you would not have it in a glass aquarium type cage or a home made wood cage with no tile or other heavy lining and seal to keep in heat and humidity right? We both keep ours in fairly sealed stacked cages designed for snakes. Not only can they be difficult to handle when they are full grown sausages but they really do not fair well in conditions that are less than perfect. One member on here ended up having to have hers treated for many months for an infection that just would not go away. We have seen many members post pictures if scale issues due to too high or too low of humidity.
Just be sure whatever you decide on that you have done ALOT of research and that you have everything you need for it before you bring it home. We are simply urging you to think it over very well before jumping into something. I would recommend a columbian red tail boa or one of more docil locality boas like a hogg island. A carpet maybe. I would not recommend any giants or the dwarf versions of them. Dwarf and super dwarf retics are very difficult to handle. They are not mean but they are very flighty and often musk when first taken out. Dwarf burmese are known to have a very wild and sometimes agressive temperament their entire lives. They usually cant be tamed like other snakes can. BCC boas (true red tails like Suriname and Guyana) get larger than than the columbians and often have a more tricky attitude.