Technically they could support all those releases on just the right Power
6 machine, configured just right. In fact, my Power 6 machines have seen
all those releases on them. Normally V5R4M5 was on there just long enough
to be the unload/reload of hardware that did not support 6.1, like my 270.
As soon as it was put on the Power 6 it went to 6.1.
And, yes, it is possible to have more than one server in your DC.
So, they probably could have done it. Perhaps they just had other
priorities with the maintenance money, like paying off LBO's.
They will not allow V5R4 to be in the same Mimix environment as a 7.2
machine. Personally I don't have a problem with that. It could be as
simple as they don't want to hassle with trying to save to n-3 to
replicate some objects.