Both a short-term fix and a long-term fix because honestly, collecting lots of stuff should be encouraged ^_^
In the short term I'd like to see personal bank slots drastically increased Guild Bank Storage size with more slots bought like the current model. The difference from the current model is bag slots are no longer mandatory unless say you're an Enchanter, Engineer or Herbalist, etc. in which case you can buy a bag slot for that profession plus one more for a total of two per bank tab. Each bank tab would have a gradual cost in Gold and players can buy up to six tabs and would have a level requirement as a prerequisite for the last four. I would recommend these prices and levels:
Tab 2: 50G
Tab 3: 100G, level 60
Tab 4: 300G, level 70
Tab 5: 500G, level 80
Tab 6: 1000G, level 90
In the long term we're talking a total revamp. In addition to the above proposals players can talk to an NPC in a faction city's bank (Either one in SW/Org) to purchase Personal Banking, which grants the player access to a number of enhanced features, some previously exclusive to Guild Members:
- Safety Deposit Box: Purchased from a Bank Teller, this item grants the player access to their personal bank for 5 minutes. Unlike the Guild Version (Mobile Banking) the Safety Deposit Box lasts for 10 mintues and has a 30 minute cooldown.
- Cash Flow: Purchased from a bank teller, it works the same as the Guild Version only the money's deposited into your personal bank. When vendoring you have the option of paying for repairs with your savings if you'd like. If you are in a guild with the perk Cash Flow (either level) you can talk to a bank teller to switch between personal or guild depositing...for a fee.
- Direct Deposit: Purchased from a bank teller, this passive skill allows players to turn on the ability to send profession mats (Herbs, Minerals, Stones, Archeology Keystones, Cloth, Enchanting Mats, Ink, Pigments, Food, etc.) directly to their bank. Players can further customize which category of items gets deposited and even which tab. This feature can be lessened, strengthened or turned off/on at no additonal cost.
- Share the Wealth: Purchased from a Bank Teller, it is without a doubt the most comprehensive feature: This allows players to access the bank accounts of ANY of their characters on the server of the same faction regardless of level. Eventually it will become Accountwide but still be faction-specific. The player can set up limits like a Guild Master as to how much money and/or items can be transferred per character, etc.
- Major Shareholder: Purchased from a Bank Teller, you can assign one character per server per faction to micro-manage much of the above perk's features.
- Gold Loan: Depending on the character's level they can borrow up to 250,000 Gold. Players set up a payment plan when they take out the loan. Players will have 90 days from the time they took out the loan to repay it it full. If it is not repaid be the end of the deadline you will have the Bad Credit Debuff and an NPC Debt Collector will follow you around, taking every Copper you earn from loot, quests and AH sales intil the Debt is paid in full. The debuff will not allow you to purchase anything aside from health/mana restoring items from vendors and repairs.
- Debt Forgiveness: A quest item offered to people with the Bad Credit Debuff. Perhaps out of pity or simply to not lose their credit rating due to your failure to pay off your debt, the bank directs you to see the King of Stormwind/Warchief of the Horde who heard about you and might be willing to pardon your debt! As you can probably imagine, there is a catch. The quest chain offered to have your debt wiped clean depends on your level and must be completed in full.
For example level 90 players will first be asked to prove they are worthy of the King's/Warchief's Pardon infiltrating six different Alliance/Horde settlements on Pandaria (will be phased for the quest chain so the enemy NPCs don't 4-shot you lol) and stealing vital intelligence. Next you'll be sent to another Alliance/Horde faction leader who'll ask you to help them decide the fate of a few deserters. After that you're sent to see Chromie, who sends you back in time to train your level 1 self in a phased version of Northshire Valley/Valley of Trials regardless of race. After that, Chromie tells you the king/warchief requests your presence and back to SW/Org you go.
The King/Warchief had been secretly following you and observed your skills firsthand, not forgetting all you've done for the Alliance/Horde. Before he can forgive the debt he has one final challenge for you: A duel with another Champion of the Alliance/Horde looking for the King's/Warchief's pardon. After defeating them the King/Warchief is impressed you won the duel yet did not kill your opponent out of respect. He then reveals the "Hero" you spared was really a criminal who would have been freed had he killed you. In recongniton of your mercy your debt with the bank is wiped clean.
...That's what I've got in mind. if I think of anything else with which to modify this idea I'll edit I guess.