implement a stash goblin ?

summon a henchman that carries your stash chest so you don't have to portal to town to empty inventory?

it was a great feature in Sacred 2. just a QOL thought

If you feel that your inventory is constantly full, that is a sign that you are picking up too much. It takes some experience to know what is worth picking up and what is not, but a good loot filter will also help.

Personally, I prefer underpants gnomes.

Nope.
This is not a game that you can introduce anything and everything for the convenience's sake. Those games are instantly boring.
There are underlying reasons that this game does not have a pet or automated trade.

Sacred 2's Stash Imp had a specific reason. Before a patch allowed players to istantly teleport to any other opened portal from anywhere in the map (and Community Patch extended this to ports), a player needed to reach a village or a city in order to load off their loot. It was a little hassle, and before Ice & Blood the Imp was a Collector's exclusive.

Sacred differs from Path of Exile, however, in being an open world. You can go anywhere, anytime in both Sacred. On PoE, on the other hand, you have a limited access to each non-story area. This also implicitly puts you on a limit on how much loot you can carry out from an area - provided you play alone and with an empty inventory, best you can loot is 6 inventory worth of items

To allow you to have your Stash in your map allows you to bypass this. A player with enough real wealth can buy enough stash to loot, say, a whole Vault of Atziri, resulting in either better revenue on the market or an overflow of Alt & Alchs by just vendoring what you've found.

It won't be even fair to use it in non-endgame zones, as you still need either a Waypoint or a Portal Scroll to TP to Town.

So no, we cannot have it here, because it is not a question of "less hassle" in PoE. TP in this game is never really "free". Well, expect using a Portal gem in a non-endgame area, I guess

I agree with majority of people here.

First an instant stash, then what?
I would be pain in the rear to click on every single item to pick it up so auto pickup.
It would be a pain to manually move items from inventory to stash so auto pickup to stash.
Selling few tabs worth of loot will a pain too so auto sell, bonus points for auto sell based on rarity or tiers of modifiers on item.

While we are at it lets add auto potions, auto walk to quest, auto attack and maybe even auto skills.

By that point you are playing f2p asian mmo not PoE.

Sorry for harsh response but even stash access would ruin economy more so when taking bots into account.

Not every design principle PoE is based on is good, but they are mostly tried and tested stable foundations for this type of game.

EDIT: ok, it was kind of unfair for me to jump form summoning stash to auto pickup, but this is one of the features that Tencent is milking for money in their regional version of PoE so there is a reasonable concern that convenience might escalate to idle game.