You can buy vivienne's stuff, and you can exchange for PSP2i stuff in the mission badge shop. We didn't get them sitting in the lobby, or the events related to them being there.
We are missing PSZERO's stuff completely. Annnd PSO2es
Other related bosses, were the MH monster, but he was taken out as teh deal broke apart. And the Shining Knight monster, but we have him anyway in our Extreme Quest.
Forest did get harder modes, as Risk explorations. The limited quest, sure we couldn't get them anyway, since gotta go fast, but that's okay. They were just crazy spawns or repurposed maps. Like we currently see with our Valentine event.
A lot of UQ's we missed are a result of content becoming irrelevant to progression, maybe once we hit the stall point, we'll see some of the non progression ones hit. We actually aren't that far away from JP. So at some point it's going to stop.