I like the variety of crafting styles that we have in the game. It's not for everyone, but the more customization options an MMO gives you the better, in my book.
Unfortunately though, ESO encourages you to wear specific armour sets to get certain set bonuses, and many of those sets can only look like one particular style. If I spent 2000 crowns to buy the Frostcaster style, I have to stop wearing my Cyrodiil's Crest armour in order to actually make use of that new style... and that seems like a missed opportunity.
I think it'd be a great idea if some of the more rare/exotic crafting styles unlocked some costume options for players. That makes buying/finding/unlocking the new crafting style a much more worthwhile thing to do, and might make people more inclined to get those styles in the first place. That way, people can have the cosmetic effect of the Frostcaster, Hollowjack, Aldmeri Dominion, etc styles, without having to sacrifice the bonuses from their usual/preferred armour.
There is already an option to preview a light/medium/heavy version of each armour style in the crown store - perhaps those could be the three costume options.