An easy "no complaints" method of getting rid of the old quests would be to lock the reward scaling immediately and wait a few months.
E.G.
if you are in chapter 1 today they will always give chapter 1 rewards even if you progress
if you are in chapter 4 today they will always give chapter 4 rewards even if you go to chapter 5+
Almost no one would still be in the first few chapters after 5(?) months and will quickly outgrow and replace the cycling quests with workshops etc.
Then implement whatever new & interesting quest system you like. The 16 badge FA interface is perfect for this. Use it to give players 16 simultaneous questlines! Some daily ones, some weekly, some long-term achievements (Give 100, 1,000,10,000 visits!) Some that change by chapter
There are loads of possibilities, and with 16 running at the same time they don't all have to be "Doable by everyone at every chapter with every playstyle" like the main events are attempting and we can have real variety!