I still posit that there needs to be some requirement or trade-off for being able to glamour stuff that can't be equipped by your current class. Since someone earlier in the thread mentioned FFXI, their Style Lock system checks for your character having the leveled the job corresponding to a piece of gear. For example, if you wanted to Style Lock the lv99 Thurandaut Boots you need to have leveled either MNK, DNC, BLU, Thief, Ranger, Corsair, Puppetmaster or Rune Fencer to lv99 so that they could equip the boots. Once you do that you can Style Lock it on any job.
Since I didn't address this earlier:
That's not what the OP said. The OP said artifact gear would be excluded from the changes he/she is asking for.
Since you're fond of pictures, here's something to chew on:Everything else? Whatever, but this "mix and match" is rather.. I don't know, I don't like it.
Out of the visible pieces of gear seen above, only 3 are native to RDM. The hat, the gloves, and the pants. The chest is the lv72 Deepgold Surcoat of Maiming (DRG), and the feet are the lv60 Sky Pirate's Boots of Striking (MNK). They look damn good on RDM, but I can't glamour them because of the current system.
If SE did what the OP is asking for, I'd be able to glamour the chest and feet on to my RDM. Now throw in other pieces that suit RDM's aesthetic but were given to other jobs; someone mentioned Amon's Hat, and I'll add the Orthodox and Dravanian Tricornes of Striking/Scouting and their crafted counterparts, the Red Thief set from the 3.1 Heavensward dungeons, and the Sharlayan Custodian's Coat of Fending, to name a few.
Moving beyond RDM, there's things like the Yamashi Dogi that is currently limited to DoL classes but am sure MNK, NIN and SAM players would love to be able to glamour. To say nothing of NPCs that tease players with mixed equipment (which dates as far back as ARR with Yda and Papalymo).
If you're worried about specific class aesthetics or immersion, that ship sailed when people were allowed to glamour reindeer suits and beach wear (to say nothing of the flood of 2B outfits we're seeing). The OP's request is a lot more immersive by comparison.