Need a g-flux spell that you resist based on character weight. Or snares based on weight. /gu"I knew I shouldn't have had that last donut"
I am also not sure that I want global markets anymore. Partially because I think it's neat to have people playing the market from one place to another, but also because I want to be able to troll local markets. Say, you have open world PvP and one of your [group's] neighbors is trying to build a stone wall, so they need mass quantities of stone. So you send your folks to sneak over to buy whatever stone goes up for sale in their local market. Neighbors lose their shit, /rage at their own players who either willingly sell to you for $$$ or put stone up for public sale because they don't know what's going on, and occasionally you mount a raid to damage their wall to sabotage progress (and/or raid wherever they harvest stone). Even better, when the price for stone in their market skyrockets as a result, people from elsewhere start trying to bring in stone to sell there. I mean, I wouldn't be TELLING people to gank those people bringing in stone, but hey, maybe we should gank those people bringing in stone...
For extra lulz, email that neighboring kingdom or whatever screencaps of the enormous stockpile of stone you end up with. Like, 50k stone that you only have because you're fucking with them hardcore.