Storage complaints are as old as the game itself. Every time new storage space was added, people just hung on to more stuff, re-creating the need for more space. It's an induced demand situation. So it's not a problem that will go away.
A workable solution is to keep items you'll use fairly often in Town Hall Vaults. This would include short term quest items, crafting ingredients, rings with elemental protection, etc
Than store limited use items in the Tower of Tremada, if you need the space. This would include long term quest items, rarely used equipment such as equipment for companions not in your party, gear for a character build that you're not using (2-H weapons for a 1-H weapon build).
That leaves your Bag of Holding for extra looting space, or for holding a few extra combat potions, etc.
As a person who like to hand on to every unique item, I get the desire to have unlimited storage space. But, really, once you have a higher tier item, there's no need to keep the weaker stuff.
Also, use those damn potions and scrolls. Do you really need to store 30 summon wolf scrolls? Of course not, those things are quickly outdated by the mid-game, so use them in the early game when they matter. Having one such scroll on you as a distraction item can help escape, sneak by a mob, but you don't need to clog your inventory with low tier items.
As of now, there are:
1) Backpack
2) Bag of Holding
3) 4x Town Hall Vaults
4) 4 house chests (two in each house)
5) 2 Tower chests.
So yeah, that's a lot of storage.