One of the things brought up a recent vanity costume discussion was how many MMO place arbitrary restrictions on what can be used in their vanity gear systems.
EDIT: The "Reasonable Restrictions" are the restrictions I could live with. I don't actually support any restrictions its more of a "what I could personally compromise with."
Given its likely at least a few months before FF14's vanity system goes live I'd like to express a few concerns about restrictions in the (likely futile) hope that Square will see and try to keep any of their own restrictions as lax and reasonable as possible.
REASONABLE RESTRICTIONS (IMO):
Combat class restrictions: Square already stated this would happen. Mages can't dress in tank armor. Tanks can't wear mage robes. Fair enough.
No seasonal gear: I don't agree and think it will annoy far more players than please, but if Square doesn't want people running dungeons in bikinis and reindeer suits for lore reasons kind of hard to give a counter argument. So long as they are aware lewd people will still dress provocatively and trolls will still mix up lore friendly gear into immersion breaking messes.
EDIT: Global Vanity Toggle Option: Basically a simple toggle switch that hides vanity gear from your PC's perspective, similar to the Hide Helmet option. This would allow players that oppose vanity systems to disable the system from their perspective without affecting everyone else (We see vanity costume, they see normal costume).
A Toggle Option would also allow players to disable the Vanity System for situational reasons, such as wishing to see their opponents true gear in PvP or encountering a player in Duty Finder wearing a costume that makes their eyes bleed. It would prevent forcing their situation needs on the general population through mandatory restrictions.
THINGS THAT SHOULD NOT BE RESTRICTED PERIOD (IMO):
Using field (crafting/gathering) clothes for combat classes: Its not uncommon to see official RPG characters wearing casual clothing over combat savy gear. A ton of players will want to emulate this trend.
"Field" gear is the richest source of causal clothing. For the mage that doesn't want robes or the tank that doesn't want to clunk around in plate mail field gear will be the easiest way to dress in something more "general clothing" in theme. So please allow using crafting/gathering clothes for combat class costumes.
Restricting gear to certain quality tiers or level: Not only will assure the vanity system will get hammered with angry criticisms the moment its unveiled, but almost defeats the purpose of a vanity system.
If someone finds a standard tier (white quality) and/or low level piece of gear they like: just let them use it in the vanity system please. I've never met anyone but a developer that thought quality tier restrictions on vanity gear is a good idea.
EDIT: No Vanity in PvP = Bad Idea: There is a small part of the PvP community that swears by this as a strategy. However a full fledge ban on vanity in PvP to cater to this minority would just annoy the general community. A better solution to cater this group of players would be a Toggle system. They could then just Toggle Vanity Off when they PvP, allowing them to see everyone's normal gear without their point of view being forced onto everyone else.