I handle this myself by playing a character that would technicaly hae been outside the standard classes.
To give a little background, Franz doesn't fall into any of the categories because he is a Garlean, and a "pure-blooded" one at that. He never had any form of aether manipulation, and would have been raised with entirely different lessons on combat, and a slew of different weapons. Within this scope, I've said he's good at using a lot of different physical weapons, but isn't particularly amazing at any of them. If there were one weapon he'd specialize in, it would probably be the axe, but that's simply because I like WAR tanking with the character.
But then there's magic, where things get much more complicated. I've set this character up to have gained the ability to use aether, but there must also be consequences for it that a normal Eorzean wouldn't understand. Conjury and Thaumaturgy are simply not possible. They require a more innate and natural understanding of using ones aether/the aether around you, and that is simply not thing I feel he should have been able to learn. To this point, arcane magic, based off of mathematical formulas fits best. (And actually, is perfect due to the reason he gained the ability in the first place). He's still in the process of learning how to apply the knowledge he knows, but without that little extra "I'll just stick aether here and make it work", not everything works as well as expected. Case in point, a healing spell or two has backfired before, he accidentally summoned a fairy and had no idea how to unsummon her, and for the love of the twelve, don't ask him to even try healing someone who isn't a hyur of sorts.
The only place where I could see a larger amount of multiclassing working together is in regards to crafting and gathering classes. Naturally, a master craftsman would probably have picked a couple fields to get really good at, but a working knowledge of the others seems passable in my book. Why shouldn't a leatherworker also have enough smithing knowledge and weaving knowledge to make their own products that much better? Or why wouldn't an alchemist have some culinarian knowledge? Both would certainly make use of similar practices and potentially have some overlap. The same could be sad for gatherers. Perhaps a that alchemist/culinarian likes obtaining the freshest ingredients possible, and gathers everything himself. It wouldn't be crazy to assume that the person could tell if some herbs, a minerals, or some fish were better quality than others.
TLDR Version: Combat should have a limit for mastery, as should magic to some extent. Crafting and gathering allow for much more overlap, unless you are literally perfect at them all.
To give a little background, Franz doesn't fall into any of the categories because he is a Garlean, and a "pure-blooded" one at that. He never had any form of aether manipulation, and would have been raised with entirely different lessons on combat, and a slew of different weapons. Within this scope, I've said he's good at using a lot of different physical weapons, but isn't particularly amazing at any of them. If there were one weapon he'd specialize in, it would probably be the axe, but that's simply because I like WAR tanking with the character.
But then there's magic, where things get much more complicated. I've set this character up to have gained the ability to use aether, but there must also be consequences for it that a normal Eorzean wouldn't understand. Conjury and Thaumaturgy are simply not possible. They require a more innate and natural understanding of using ones aether/the aether around you, and that is simply not thing I feel he should have been able to learn. To this point, arcane magic, based off of mathematical formulas fits best. (And actually, is perfect due to the reason he gained the ability in the first place). He's still in the process of learning how to apply the knowledge he knows, but without that little extra "I'll just stick aether here and make it work", not everything works as well as expected. Case in point, a healing spell or two has backfired before, he accidentally summoned a fairy and had no idea how to unsummon her, and for the love of the twelve, don't ask him to even try healing someone who isn't a hyur of sorts.
The only place where I could see a larger amount of multiclassing working together is in regards to crafting and gathering classes. Naturally, a master craftsman would probably have picked a couple fields to get really good at, but a working knowledge of the others seems passable in my book. Why shouldn't a leatherworker also have enough smithing knowledge and weaving knowledge to make their own products that much better? Or why wouldn't an alchemist have some culinarian knowledge? Both would certainly make use of similar practices and potentially have some overlap. The same could be sad for gatherers. Perhaps a that alchemist/culinarian likes obtaining the freshest ingredients possible, and gathers everything himself. It wouldn't be crazy to assume that the person could tell if some herbs, a minerals, or some fish were better quality than others.
TLDR Version: Combat should have a limit for mastery, as should magic to some extent. Crafting and gathering allow for much more overlap, unless you are literally perfect at them all.
