I build display systems for collections and if I were you I would think about a multiple smaller displays.
Otherwise, that's going to be a HUGE display case, if you allocate about 9" width per figure that 3rd row would require a case wider then 8 feet.
Plus if you go with a single unit, you either have to wait until the collection is almost full or you will have huge empty areas.
You could go a different way
Perhaps one for the original 7, another for the conceptual/repeat armors, one for the HPP and one for everything else?
You can also do a mix of shelves and cabinets, you're really only limited by your budget and from personal experience it is easier on the budget to build multiple small displays instead of large singular units.
PS- I don't know your collecting mentality but I personally don't have a problem selling figures that are upgraded. For instance, when I buy the die cast mark six I will sell my original.
I'm sentimentally connected to the idea of the collection, not the physical items in the collection.