Actually, on most bedrock, you would be just fine with 13 TSF. I have regularly designed foundations on limestone bedrock with allowable bearing capacities in excess of 100 ksf (50 TSF). That is allowable, not ultimate. Soil, though. Soil would start to be a problem for mechs. And that is what they would have to walk on across most inhabited planets. Common residual silty clay soils you can expect to be able to support around 1 to 1.5 TSF. If your vehicle of choice is going to exceed 1 TSF of ground pressure, you will have problems as a flexible military vehicle. This is why the late WWII concept of the super-heavy tanks never went anywhere.
But, again, it's always messy and fruitless when you mix Battletech / Mechwarrior with real physics and engineering.