Hi!
As for the idea of allowing you to design your own looks - no, definitely no.
First of all, such a feature usually results in a lot of boredom, as people are likely to run out of ideas in the middle ground - you will have the Adonis faction and the leprosy faction, and a dwindling middle ground of humans that actually look like human beings.
Secondly, Dwarf Fortress strives for a high level of consistency. We already have genetics working in Fortress mode and dwarves are beginning to have a life before the fortress. It is only reasonable to assume that adventurers will also eventually be completely embedded in the world of Dwarf Fortress. That is, they have parents, grand parents, cousins, and what not through the centuries. And they will inherit traits from those before them. So, it would be counterproductive to allow free changing of the traits.
However, once we get things to such a level, you might suggest that you are offered an adventurer, and if you don't like him/her, you can ask for another youth to be suggested. That is the system basically used in the Lunatic Dawn series, which also have a consistent world, but a much, much cruder simulation.
As for the beauty question in general, I want to add that there is the ancient saying of "beauty lies in the eye of the beholder". And I agree with Cganya that there is probably a bit of immaturity involved in some of the assumptions about beauty.
However, I think what may also be involved is the current format of the description texts. They list a lot of details in a big block, and some of the markers get repeated quite often. I found the frequent appearance of "somewhat" slightly annoying myself. So, it may be more a problem of interface design/presentation rather than actual beauty/lack of beauty.
Deathworks