In relation the post, I am not sure why gear swapping is the norm of MMORPG or RPG genre. I've played EQ, GW, FFXI, WoW, LOTRO, Vanguard, RO... the list goes on, some of them I don't even remember. What I do remember though is that choosing your gear wisely prior to the encounter was the norm in the games I've played, FFXI was the only one that really allowed full scale gear swapping and the community built their strategy based on that. So, in this case, I actually don't see gear swapping as the "norm" of MMORPG.
If you are talking about RPG in general, I am not sure which RPG is so hard that the majority of the community take gear swapping in mid battle as the norm. I've played my fair share of RPGs and listing them would just be silly. So I actually don't see your argument of "Gear Swapping is common in RPGs." as a legit reason why gear swapping should be allowed in FFXIV.
As of my personal opinion, I think both "gear swapping" and "choosing your gear before the encounter" takes time and efforts. However, I much prefer the latter. "Gear swapping" to me is like memorizing the text book before going into the exam, does it take a lot of effort? Sure does, and I applaud the people that have the determination to do so. However, "choosing your gear before the encounter" or choosing your gear based on the mechanism of the encounter and balance it with your playstyle takes real understanding of the mechanism. You have to break down the abilities that you may encounter, think about how you would prefer to handle them, then build your gear set around that prior to engaging. Sure, you may have to sacrifice a thing or two along the way and be a little "less perfect" but to me that's where the fun is. You can choose to further strength up your playstyle with the gear or you can choose to patch up your personal weakness with the gear instead, this decision to me is fun.
This of course is how I play and you may feel different and that's fine. Ultimately, whether gear swapping will be implemented or not is up to the devs.
The fact that you can't select a set of gear that will handle a battle with different variables is exactly the beauty of choosing your gear wisely prior to the battle. You need think hard and find what set of gear will suit your playstyle and the encounter the best. Perhaps the fight has a lot of fire damage, but you are confident with your own skill that you can dodge them all, then why not stack up on allowing higher damage output? This way the boss goes down faster and you will ultimately ease some of the burden of the group. If you don't think you can dodge all the extra fire damage, then wear fire resist heavy gear, even though this may reduce your damage output, but being dead means 0 dps, so you go for survivability. Choosing your gear prior to the battle isn't a cop-out to not wanting to carry more gear. It takes real understanding of your own playstyle and how it fits into the group's playstyle and of course how the encounter works. In this case, bringing every set of gears available to encounter every variables in the battle is the easy way out. Sure it takes a lot of effort to gather all that and write up the macros. However, you are just playing reactively, what's the fun in that?