Depends on the corporate i suppose.Nope mate your reading this wrong you cannot improve corporate well enough without extending out to make room ..it will cost huge amounts to do the groundwork for and decent corporate additions and they will be idiotic not to hoy in some seats as part of the build ..what you describe will never happen but its your opinion and your welcome to..... it Oh and "I think a sensible thing for them to do would do enabling works to make it easier to add extra seats/tiers in the future" is what Bob Murrey thought in 1997 and luckily he did then the sol was designed for easy expansion and will only need some tinkering to add more corporate room to the design.Personally i think the 250 million was of the top of burwells head (hes a bulshitter)and could be done for much less than that!
Assuming the east stand is already pre designed to go out as far as the north did to add the extra tier on.
You could have a level at least as big as the bcb and full length of the ground to do a fair bit with.
Then a concourse for extra normal seats.
But I agree its not as simple as some people think.