So if understand this right
You get achievement, get an armor set, glam it, toss it out
Then you get a new gear you have to spend time to go get the gear again and tossing everything?
I do not think so, Just get rid of inventory management from retainers and make a new system that can be expanded on if it is true they are limited to 175 items. If retainer limits are the problem then put inventory management on something else, like a bank chest, this shouldn't be hard.
It is not "something" it is them trying to give a bare minimum and hoping people be happy with it.