It was a long time ago now, but I'll be honest, I can't recall the Contractor installing additional piles to accommodate an extension of each stand.Our stadium was built with stronger foundations under 3 sides to enable the capacity to be increased from 10100 to 18000 if required by putting extra tiers on those areas and filling in the corners. It is not very likely we will need that any time in the near future but if we do, it can be relatively easily achieved without having to move.
You have the space at the CCS, so that is the biggest hurdle, but make no mistake, expanding a structure is a big and expensive job - as you add rows above a certain height, the costs start multiplying (obviously, the further back you go, the higher you go, and the more weight of steel you are adding).