Like Mabinogi? No, let's not do that.
Mabinogi basically gave you one extra bank slot per character, you could create 100 characters per server. Or you could buy pets. Pets don't get a bank slot, but you could summon them anywhere. There was a strategy known as "pet roulette" where you'd quite literately summon a pet, hit the monster, and unsummon it, all within 200ms, and the AI was too slow to respond to this. Of course Nagle had to be turned off to pull this off.
My preference in this game would be to stay the hell away from that. 100 characters @ 12$/char or pet value = $1200 invested in a single account, that you could do in one day instead of over 5 years. That is as much as buying a new PC or Smartphone every year. Or more than what typical drinkers spend at the bar over the same time. There is something terribly wrong with MMORPG's when NONE of them teach people to not be a hoarder.
Though I suppose digital hoarding is preferable to people hoarding trash and pets in reality.
How I'd solve the inventory problem AND the glamour log problem is a lot more simple.
1) Remove the "store" from the retainers, only one retainer can be assigned to be a market NPC, all others must be stationed at your Inn, Apartment or FC house in order to access the common inventory.
2) Remove the "inventory" per-retainer (you can still dress them up), each of them only have "one bag" of inventory and items here are from ventures and must be deposited in the common inventory or they can not be sent out on another venture until the retainer inventory is empty.
3) Create a "common inventory" that only the retainer can access directly. When you call the retainer anywhere in the field (not just bells) they show up and ask what task you would like them to do:
By which...
a) Retrieve or Deposit Currencies (Gil, Tomes, Scripts, Beast Tribe tokens)
b) Retrieve, Deposit, or create Consumables (only if Retainer assigned to Culinarian or Alchemist, or Player has these skills)
c) Retrieve, Deposit, Repair, Glamour or Create/Desynth Gear (only if Retainer is assigned to a crafting skill that can create, repair or desynth gear)
d) Retrieve, Deposit Furniture
e) View retainer attributes and gear
f) Reset retainer, or change task list
g) Just follow me (I need you to model/pose for a screenshot or video)
Separating the consumables from the gear solves a stacking problem, because a lot of crafting involves multiple layers of consumables, and when you have multiple retainers currently, these may end up on different retainers.
Retainers can be assigned to the following tasks:
a) Shop keeper (1 Market, and 1 "Housing shop"), and one can be assigned to "Market Buyer" if designed
b) Any DoL, including jobs we don't have that are specific to Retainers, like "Sheparding" or "Farming" where you supply the retainer with the seeds or calves of what you want to grow, and they attempt to grow more of them.
c) Any DoH, can synth or desynth any recipes that the player has already done at least once.
d) Any DoW/DoM class/job, limited to the level the player has reached.
If you have more retainers, you can of course assign them to more jobs. But only one can be assigned to the public market. The number of items that can be put on the market depends on the "experience" level of the Shop Keeper job ( 1 item per level, starting with 10, capped to highest level player has achieved.) A Retainer assigned to "Market Buyer" will be given a list of items to buy and at what price to buy them at or lower. Shop keeper will sell items at the price requested. If a Shop Keeper and a Market Buyer are both assigned, then they will not deal in the same items. So if you need X quantities of A B and C, but you only want to pay a certain amount for it, they will buy any items listed up to the quantities listed, or until the budget is exceeded. This also gives a way for sellers to look at the market and see what is "wanted" and not merely the wishlist.
The common inventory is pseudo-unlimited. Instead of a player-style inventory, you get something more like the crafting menu for consumables, where you have a list of everything you have, and what you can craft with it on the other side. So you can either retrieve/deposit things (unlimited stack size, or 999) from one side, or you can craft things from the other side that you have the items for. For the gear menu, it's the reverse, you get a list of all the items "you have deposited", maximum stack size of 1, but can be dyed or used as glamour without removing it from the common inventory. On the other side, you will have a list of items that you haven't found or can craft (based on crafting materials deposited.) Once you find one gear-slot item (eg a tank gauntlet) it unlocks all the items that fit that gear slot from that gearset, regardless of class/job. Non-craftable items (eg Raid items, Tome items) obviously can't be crafted, but if dropped on the gear log, will let you exchange like-for-like, hence no duplicate items.
This gives players an incentive to quite literately "drop all the junk they have" on the retainer and the retainer will manage it for you.
I know some people will not like the idea of a reduction of market presence, but I think that is something that needs to happen because of how much time is wasted in cycling through retainers just adjusting prices or whatnot. There should only be a single retainer on the market per player, and the number of items they can sell should be reflective of how long they've been selling items, not an arbitrary value. 1 retainer that can list 80 items is better than 4 retainers that can list 20 each.
Pulling from the "freemium" playbook...
I would not object to having the common inventory (and currency bank) have a stacking limit that can be unlocked. Say the default stack is 99, but you could pay $20 once and unlock it to 999 for both items stacks you can sell and items you can store. Mostly just to keep RMT in check by limiting the amount of items that create large gil numbers.