Skip,it's reported elsewhere that some improvements are planned for inside T3 which should improve passenger experience.
As regards the absence of MON from T2, are you assuming that few of the MON slots will be taken up, or if extra based a/c are required to utilise some of the slots they can be accommodated by the carriers in T1 or T3? There has been discussion on the capacity issue previously that if, say, 4 more based a/c (compared to the 9 MON based) were needed by T1 airlines, whether it would require an airline moving all or at least part of its operation to T2. I agree that unless MON's 9 based a/c are replaced by 9 others, the net impact would be less based a/c so in theory less congestion at peak periods and a better passenger experience.
However, even this doesn't take into account natural growth that was planned anyway.
I understand easyjet and Jet2 were both planning an extra based a/c - unless that had changed.