Grimgar of Fantasy and Ash
I would love to do this, using PATHFINDER rule set. I don't know how many people would like to be involved but a dozen or so players, who have a base city of operations, that can switch out players would be excellent. So not a set party, adventuring here and there, hunting BOSS like people/monsters for rewards, guilds that we pay to GO UP in level, or acquire new skills. This would be awesome.
Again, using pathfinder rules. It doesn't have to be Grimgar proper, but that anime definitely spawns the idea. Great show.
I'd like to read other people's take on the idea.