Just how much more do you need?

You can have up to almost 400 slots to store items already, then there's over a dozen other places you can store items as well through various NPC's/moogle slips. They have already stated they are looking into possibly adding a new container--it's not too far fetched to expect that to happen with the new expansion, as they have a history of introducing such things with an expansion. Besides, you typically won't be carrying all that stuff in your active inventory at once---the unneeded pieces can be stored in satchel/sack, or possibly even be left in safe/locker/storage depending on your plans for your play session. For instance, I have a set I like to use on BLM and WHM specifically for Campaign/Besieged use sometimes--I don't have to tote any of that gear for doing physical damage around when I'm doing non-campaign/besieged activity.

If you're asking for more than 80 per container, for now you're likely S.O.L due to limitations in the base code inherited from the PS2 that SE insists on maintaining across all clients. This is not conjecture, it was confirmed by SE to be an issue a long time ago, and the claim was vetted by people who poke around in this code all the time (think the actual limit was actually 83 or something, more than 80 but not 85). With a little creative tweaking and cutbacks elsewhere in the UI/background processes they MIGHT be able to bump it to 85 without too much impact, but they are not willing to make those trade-offs.

That is the problem with the legacy support at this point....many matters cannot be enhanced/introduced because of SE's insistence on extending legacy issues across all platforms to keep development and play "balanced". Until SE changes their position on this issue and starts rewriting core code...need to be a little more vigilant on inventory management if you are wanting to hoarde all that situational stuff. For instance, might have to sacrifice mog decorating for a Panatiere and a couple more pieces to cap your storage container with as few pieces in your safe container as possible. Get moogle slips and store all the abby gear for the jobs you rarely use anymore. Make more sensible choices in gear that you carry based on what you plan to be doing... Somewhere, somehow, common sense needs to prevail.