Just because something is possible doesn't mean it is easy. Converting the 86 or so talents involves coordinating with dozens of artists and riggers at once, it's a stupidly huge undertaking. That's not even considering the amount of outfits you'd have to include for each talent. Think about how expensive it is for one talent to get top tier rigging and art done for a new model. Now multiply that by 86. Might as well double or triple that to account for all their outfits. It's why shit is done in piece-meal and moves as slow as a snail.
On the flip side, smaller corps like Phase don't do immediate shifts like that all at once, despite having smaller talent pools, because they don't have as much cash on hand to throwaway so easily.