A "stash" that is only accessible outside combat mostly preserves that balance, IMO.

Most games come up with a range of ways to get around the problem, even when they do have a strictly limited inventory with encumbrance:

• Zero weight quest items

• Ability to run or fast travel while encumbered (FO4 selectable perk)

• A pet or NPC capable of carrying your less valuable stuff back to the vendor for sale (Torchlight had this, did Diablo? I haven't played in decades.)

• Pack animals/robots

• Portable vendors (Skyrim had a demon vendor you could summon once a day)

• Bags of holding (or similar)

• Warp chests (many chests with same contents/inventory around map)

etc. ad infinitum. The fact that most games implement a variety of ways to deal with absence of an infinite inventory is kind of a tipoff that it's more of a burden than a desirable aspect of gameplay. Most of these games are holding up a carrot (or several) to get you to pursue certain achievements just to reduce the monotony of inventory management.