Here is another rugged robot platform that is ready for your complex projects. The WT-500 Tracked Robot has a 304 SS body and max load of 30kg. It can climb 30-degree slopes. The max speed is about 1.5m/s. The WT-500 comes with a 40mm wide track.
The WT-500 is IP54 rated. It has a low center of gravity and allows for a second level.