With all the extra gold laying around, I came up with this idea to be able to buy buffs from the merchant. Half-hour potions that give a boost (only one useable at a time). For example a battle potion that gives +critical, +critical damage, + STR, + double attack. A magic potion that gives + cast speed, + all magical damage, + INT + all spell schools. A luck potion that gives + magic find, + gold find, and higher chance to find rare mobs. Or a stamina potion with + max mana/HP, + defensive skills, + resistance. What do you think?

Maybe. How about an auction house? haha

I think an auction house would increase hackers ingame. To counter that you could make a gold cap, but eventually the economy would inflate and people would charge max gold for everything. However, I would love to pick up missing set peices And I have like a billion martyr's shivs to sell.
Or maybe not. Since there is no pvp, people won't really care to charge high prices because there is no competition or scarcity outside of the leader boards.