Since a lot of quest gear is not limited (which I thought was the key to having something being sewable) they can be altered.

My herald had a pair of bracers for example for pretty much 400 hours. Neltouda saw me, took them, and gave them some cool description. Didn't change the attributes or that I could wear them, just made them look unique.

And I thought that was a very nice touch, something I would actually like to see more of. A custom tailor in herald would get a lot of use I think- even if he could only do it to non-limited gear which is generally not as powerful as limited gear. (so as to not disguise what limited item it actually is)

Ie. I would probably find a passable piece of non-limited eq and have it embroidered with my char's family crest or something for RP purposes, even if it meant giving up the stats from slightly better gear.