Add-ons are installed by the user and can indeed be changed/improved/upgraded through firmware (as with the extra modes added to the De-esser with V1.5).
It’s just the installed/not installed status which is unaffected by changes or updates. e.g. you do not need to re-add all your add-ons after a factory reset.
Yeah – what’s missing is a “de-authorisation” mechanism. Stops the 3rd party trade of plugs I suppose and protects revenue for A&H. Fair enough but I do see why the OP would want this. If I’d bought a load of plugins and then wanted to change to an SQ6 or 7, or a new SQ5 with no scratches or faults, I’d be a bit sad.
I dare say if you could show that the old desk was beyond repairable, A&H support might be swayed!