Maybe we're trying to solve too many problems at the same time. In analogy with Purchase Fuzzies and Utilons Separately, I'd guess that the activity that best promotes physical fitness isn't the activity that best trains transferable skills isn't the activity that is the most fun, so spending some time on something intended to improve physical fitness, some time on something intended to train transferable skills and some time on something intended to be fun is probably better than spending a lot of time on something that haphazardly tries to achieve all three. (Also, which activity is best for a given goal is likely to vary from person to person, so beware of other-optimizing.)
Training in organized sport often gives you the benefit of increasing physical fitness, even if it isn't the core of that particular sport. I play baseball and some part of our training is increasing our general fitness, even if we don't particularly need that in the field.
Apart from that, I think you might be on to something.
This post is a bit of an experiment; Most of the time, Discussion post lay out an idea and this idea then get commented upon. This post, on the other hand, will be purely about discussion on a topic. If this works out well, I'll might post more of these in the future.
On to the meat of this post:
I got this idea from a reddit post on /r/LessWrong.
To quote:
So have at it.
I only ask for one thing and that is to hold off on proposing solutions for 24 hours before giving suggestions for actual sports. In the first 24 hours, please discuss what makes current sports unappealing to rationalists and what aspects a sports designed for aspiring rationalists should have.
Edit: The 24-hour window has closed and solutions and suggestions can now be given.