I'd just go with an albino boa....I would not recommend a retic for some ones first large python...They have a deserved reputation for being mean and although it depends on the individual, why take that chance when there are plenty of calmer on average species? The same goes for GTP's and Amazon Tree boas. Beautiful for sure but most will take regular work to tolerate handling. It may be a little small but I've always been a fan of king snakes, Mexican black kings are stunning and are very docile. A nice high orange pueblan milksnake would be good if you want color.
I don't entirely disagree with you. A mainland retic is definitely not a good snake for someone's first snake because of the size that they grow to. That's why I recommended a super dwarf. Females rarely get longer than 8ft and they are extremely slim snakes for their size. I've seen female ball pythons thicker than an 8ft female superdwarf. I am a huge retic fan though and believe that their reputation in the past is definitely holding them back today. You find more docile retics these days than you did 10 years ago just b/c of captive breeding. Mexican blacks are extremely stunning. Nothing is cooler and more mysterious than an all black animal. Personally, I would rather go with the black milksnake though b/c they do not even require a heat source because they like their temp in the 60's and low 70's b/c they live in a very cool environment and they get thicker than the black kings. Watching them transform from red to black is pretty sweet as well.