I kind of like the idea of all bright blue accents.. might be garish but oh well.

My opinion in the seatpost is that you are going about this the wrong way. It is the biggest mistake to adjust saddle position when it is the handlebar that should be changed. You must find the correct saddle position relative to the cranks and start with that. Then you should change the stem and handlebars accordingly. This may mean a 130mm stem with the longest reach bars you can find. If his torso is proportionately long than his legs are proportionately short and a set-back seatpost will only serve to make the position even more awkward as it moves him further and further behind the cranks.