As I recall, your primary complaint with my inventory was the lack of Dark Magic Skill gear. Frankly, I was still being very generous with that set. An ideal RDM isn't ever, ever going to keep their full Nuke sets and staves out while they have their TP/WS sets and Swords out. Why? Because we have a Mog Sack and a Mog Satchel for those things.
RDM changes roles in the field. Even with only 80 active inventory, you have plenty of room for things that you are going to need available to you *At any one point in time*. If the situation changes and you need to swap to staves and grab your Nuke sets? Chuck TP/WS/Swords into your Sack and grab Nuke/Staves/etc out of it. It takes 30 seconds.
Here's the thing: Warrior is only good at one thing. Being a Warrior, aka Hitting stuff. Black mage is only good at one thing. Being a Black Mage, aka nuking shit. Red Mage is good at everything. Can you reasonably expect Red Mage to be better at blowing things up than Black Mage? No, but it is (was). Sorry, BLMs. Prior to Elemental Celerity and the crapload of Nuking buffs BLM has received post-Scars of Abyssea, RDM was clearly the superior nuking choice.
Can you reasonably expect a Red Mage to ever be able to Melee DD as effectively as a MNK, a NIN, a WAR, or a THF? No. Never. Not in a million years. Why? What can that MNK, or NIN, or WAR do aside from DD effectively and tank? Can they Nuke? Can they heal? No. These are specialized jobs, who excel at their chosen function. Red Mage is not a specialized job concept. It is an amalgam of different specializations that it can swap between in the field.
No matter what, all jobs and roles in FFXI are always best played via specialization. Specialized DDs are the strongest DDs. Specialized Healers are the strongest healers. Specialized Buffers are the strongest Buffers.
Red Mage is not a job designed to be able to do everything at the same time. Red Mage is a job that is designed to be able to change its specialization, and occasionally utilize multiple, mutually appreciative, simultaneous specializations, without changing jobs.
Can you heal, buff, Dia, and DD effectively at the same time? Hell, I hope you can, easily. Healing, Buffing, and the Dia spell are acceptably proficient without the use of the Main/Sub slot.
Can you heal, buff, Nuke, and DD effectively at the same time? No. Why? Nuking and DD'ing conflict. You cannot use staves while DD'ing, and you cannot nuke effectively in a sword.
What does this mean? If you're doing something which obviously conflicts with another potential specialization, store the gear for said specialization in your sack/satchel. If you suddenly need to disengage and start nuking/kiting, toss your DD gear into your satchel and grab your Nuking gear out of it. I'm sure you can handle autorunning for 30-60 seconds while you spam enter and scroll down, right?
I really don't want to see the "I want Hybrid Gear that's better than all the specialized gear combined" argument brought up again, but it's not like its gained any more merit since the last ten times it's been thrown out. Keeping conflicting sets out at the same time is stupid. There are some sets that should never, ever be stored, like PDT, MDT, and Refresh/Idle. But really, why the heck would I need instant access to my HMP set if I'm in Abyssea? Or my Bio set if I'm using Dia on everything? Work smarter, not harder.