Alright so here is what i am thinking....
people are bored because there isnt much to do but there wasnt much to do from the very start a way they could fix this is by adding more cutscenes to the game???? idk how that works but base pso2 had a TON of side content where you got to know and interact with a ton of recurring and sometimes non recurring characters... this makes the player feel more solid in the game i think and even when they get through all that content they will come back for more just to be around the characters

another less important thing would be a new type of weapon drop. these drops would only drop from specific vet bosses in their specific areas.
an example i thought of would be if you defeated a dread level thunder banser in West aelio you could get a weapon i would call the lightning claw. this would be a katana weapon with potential that adds a large amount additional lightning damage atop its base damage but only for a certain attack. these kinds of weapons would look really cool and be kind of a standalone that maybe you wont be able to make in multiweapons but wont be held back by that due to their power

also making sg scratches available to trade would be nice because i think some of the items from before january would have some value eventually