As it stands, Asteroid Fields are bland and only useful to farm common ores, which is kind of a waste of their potential. To make Asteroid Fields fun and interesting to explore again, I'd recommend adding a lot of features to them. Depending on the level of star system add appropriate levels of ore. You can still have Copper, Silver, and Gold, just add things like Durasteel and Titanium in smaller amounts depending on the system. Also add the random locations again. There could be stuff like abandoned mining bases, small hideouts, maybe even wrecked spaceships that belong to factions like Cultists, USCM, Miniknog, etc. Also, perhaps with the addition of an item like a Gravity Generator, you could build functioning bases with gravity and airlocks and all that cool stuff! It'd be fun to set up a little base in an Asteroid Field to teleport to and mine for materials. I understand this would take a lot of time and hard work to implement, but it would make Starbound even more awesome =3
