This is not possible if its done client side, because of the PS2.
However if equipment sets were to be stored on the server .... anything is possible

If you could equip a set of armor, and "save" it to a server storage equipment macro, you could also recall it.

It could fix the problem, but you might see a partial loading every time you call one of those macros.
Still, given that you can load all your macros at once in about 3 seconds from the server after saving, I don't see a problem with a 1-2 second delay when calling an equipment set change macro.

This could also lead to a method that pulls data from the Porter Moogles to be able to summon a set of your favorite armor, rather than piece by piece. Like "Withdraw saved set 8" or something.

I think this is going to have to be the future of FFXI, saving things on the server instead of the client. The PS2 doomed everyone, but in 2003 who would have known the game would go into 2011 and still be popular? Most PS2 online games have had their servers shut down, the fact that EQOA is online still is nothing short of a miracle.