Why do we even need an "alternative" form? I am satisfied with how characters are developing, I am overjoyed gear swap doesn't exist, and I am pleased that in 2.0 mannequins will exist that function as gear holders for easy and efficient equipping.
All I see in these repetitious gear swap threads is pretty much "it was in XI, lets find a way to put it in XIV." I understand your post is examining an alternative to it; but you're still looking at putting in a system... simply because it was in XI.
I'd be super happy if they came out with a cosmetic outfit system as you are describing, but not for the sole purpose of including gear swap.
In general, gear swap was a terrible mechanic of XI that created a plethora of problems that were not able to be fixed during the entire lifespan of the game. I think even the proponents of gear swap understand the logistical nightmare it continued to impose on the game. I don't want to see a repeat of inventory overload, constant blinking of characters based on the attack I am about to use, macro hell (especially given how terrible macros function in XIV), or even party restrictions because I don't have 20 pieces of gear for each of my 10 attacks.
I think a better question to ask the forums would be "why do you feel it is necessary to promote a feature like gear swap?"
Do you think there isn't enough character customization? Do you feel the character progression isn't satisfying enough? Do you desire more skills? More diversity? What is it that you REALLY want out of gear swap or a system that functions along the same lines? I haven't heard a solid answer throughout all of the gear swap threads except "it was in XI."
Talent systems add alternative advancement for characters and can be used to introduce new spells, FUN spells, character advancement, and easy swapping for fights. If made correctly, a good talent system eliminates all the issues of gear swapping and allows for a diverse makeup of characters. I am sure now that I brought up talents, someone will bring up merits. Merits are a form of a talent system yes. Unfortunately they lacked the proper means to increase diversity and instead increased the amount of elitism and classism that existed in XI. Didn't have the right merit? No party invite. Furthermore, merits were just horrible reason to add another insane amount of grinding to a game that clearly had enough. I don't want to see merits either. If XIV can improve on merits and create a brilliant talent system that promotes diversity, eliminates the classism regarding merits, and removes the grind associated with merits then yes I'd be elated to see such a system.
I am pretty happy without talent systems, or merit systems, or even gear swap systems. Someday I think I'd like to see an introduction of talents -- certainly not in the form of merits and definitely not in the form of gear swap.
As I close this post; let me give you some food for thought. If you really want gear swap... the materia system does exist. In fact, you have the option to meld several pieces of materia to one piece of gear. Simply meld to your hearts content and swap that gear BEFORE battle starts.
Couldn't have said it better.