I've dealt with... a few changes in form with Chachan. To the point that for a little while he thought all girl Lalafell spent some portion of their life as a Miqo'te. He's also dealt with a couple characters that have changed multiple times - one of whom has gone from male to female, and then through basically all the races. How have I handled it? I just... roll with it, I guess.
Even if it's not "Fantasia," people will provide all sorts of alternate explanations for the sudden change. Something as nebulous as "a potion" to an aetherical accident to glamours to ticking off a Sylph and being "cursed." And, if I want to RP with them, I have to have Chachan deal with the fact that they're a different race or gender (or both!). Unless it's a situation where they've "been" that race all along and have just been waiting for HW to update their models (had a couple folks playing Au Ra and just had us pretend they had their horns and tails), the first and foremost thing is that Chachan will likely not recognize you if the change is drastic enough. He might (slowly) catch on if he recognizes your mannerisms, but otherwise you're going to have to tell him.
I get that having Fantasias readily available ICly would spell disaster for such things as espionage and criminal activity. However, so would being able to get a Sylph to change you or casting a glamour that makes you look like another person. I just see it as folks having a bit of lighthearted fun... and exploring their options. Maybe they picked a race and - either through plot or play - decided they didn't like the race, but also didn't want to lose all the friends their character had made. Some sort of convoluted thing to explain the why and bam - new race. Hopefully they'll be happy with what they chose and stick with it - or they'll go back to their original race and the entire event can be left to become little more than an oddball memory.
Personally, I've only used my Fantasia on Judge - who I had been playing as in disguise since inception. His heavy armor, I think, really helped with that... so the change likely wasn't that obvious. Beyond that, I used it to make Gogon taller since I wanted a height difference between the two brothers. Which I waved away as him always being that height.
Transformation/disguise/reveal plots are not all that uncommon - especially, apparently, in the realm of FFXIV RP. The best approach to it, in my mind, is to either avoid it or roll with it. "Rolling with it", of course, being subjective and ranging from applying your own headcanon to the situation or straight up going with what is being presented.
Even if it's not "Fantasia," people will provide all sorts of alternate explanations for the sudden change. Something as nebulous as "a potion" to an aetherical accident to glamours to ticking off a Sylph and being "cursed." And, if I want to RP with them, I have to have Chachan deal with the fact that they're a different race or gender (or both!). Unless it's a situation where they've "been" that race all along and have just been waiting for HW to update their models (had a couple folks playing Au Ra and just had us pretend they had their horns and tails), the first and foremost thing is that Chachan will likely not recognize you if the change is drastic enough. He might (slowly) catch on if he recognizes your mannerisms, but otherwise you're going to have to tell him.
I get that having Fantasias readily available ICly would spell disaster for such things as espionage and criminal activity. However, so would being able to get a Sylph to change you or casting a glamour that makes you look like another person. I just see it as folks having a bit of lighthearted fun... and exploring their options. Maybe they picked a race and - either through plot or play - decided they didn't like the race, but also didn't want to lose all the friends their character had made. Some sort of convoluted thing to explain the why and bam - new race. Hopefully they'll be happy with what they chose and stick with it - or they'll go back to their original race and the entire event can be left to become little more than an oddball memory.
Personally, I've only used my Fantasia on Judge - who I had been playing as in disguise since inception. His heavy armor, I think, really helped with that... so the change likely wasn't that obvious. Beyond that, I used it to make Gogon taller since I wanted a height difference between the two brothers. Which I waved away as him always being that height.
Transformation/disguise/reveal plots are not all that uncommon - especially, apparently, in the realm of FFXIV RP. The best approach to it, in my mind, is to either avoid it or roll with it. "Rolling with it", of course, being subjective and ranging from applying your own headcanon to the situation or straight up going with what is being presented.