I'm not sure all of these are tied to PS3, especially stuff like inventory and towns, that sounds like server issues(the towns not sure maybe some spaghetti code in there, heavensward has areas that are way way bigger than cities and Ishgard itself is split into 2 but each area is like larger than Uldah combined it feels like). Minion+chocobo I'm not sure what's the issue, you mean like the cosmetics pets shit? The only issue with chocobo I remember is having them out+mounting but they fixed that in Heavensward.
I think mostly it's gonna be a matter of letting them do larger rooms with more stuff going on during boss fights, and develop on world boss content like hunts or the treasure hunt island exploration shit they added in HW. PS3 really couldn't handle shit with a lot of people, so they had to tone down some aspects of it, like amount of mobs, mob abilities and loot availability.