I am not sure that I like the idea of raising the pitch, probably because of Old Trafford. So, you are saying that extending the upper tier is also not possible, if we can't add another tier?
A third tier would have to be steeper than the second tier to see the nearside edge of the pitch, which as it stands can't happen because the second tier is at the maximum permitted angle (34deg).
So it's either re-build completely, re-build the second tier at say 32deg (but this will adversely affect the view and might not work) and add a third tier at 34deg or, add a third tier at 34 degrees and raise the pitch to change all the sightlines (which again, might not work because it's a long and tedious set of calculations which I haven't worked out).
Or stuff it, break the rules and build steeper than 34 deg - anybody been in the back of the Bernabeu?
Whenever people fling around figures from 70-80k, apart from transport issues one thing I always wonder is at what capacity do local residents get to veto any plan purely based on the detriment to their living standards? Is there a figure? Would they ever have the power to oppose it? There was plenty of opposition to the Annie Road stand.
I don't think there was actually (this time round) - like anything else you'd have to see what a planning application would bring and what other benefits there would be. Or in planning terms, what 'benefits' would justify what 'harm'.
So far, I'd argue redeveloping the ground has done more good than harm to the area however contentious that sounds.