i think it would be better to see what players had to offer in terms of design because anet design is lacking. put the winning designs in the gemstore.
I wouldn't say Anet's design is lacking - there are tons of amazing outfits, weapons, creatures and mounts in the game after all - but any design contest would be amazing nevertheless! They tend to spark quite a bit of interest in the playerbase.
I really loved the design a weapon contest a couple of years ago, as well as the way the winning weapons were introduced into the game.
The stories we love best do live in us forever. - J.K. Rowling
If a design contest is implemented then there needs to be restrictions on armor clipping with weapon boundary boxes
See past restrictions from the weapon contest https://wiki.guildwars2.com/wiki/Design-a-Weapon_Contest