That is what I describe as the "package" of reforms, yes.
> The thing that would help that is a constitutional amendment prohibiting court packing.
Good idea! Pack the court, and in that law, include a trigger provision that repeals it as soon as said amendment is passed.
(This has similarly been proposed in gerrymandering.)
Except then the other party just packs the court again instead of passing the amendment, whereas if you already have the votes to pass the amendment then you would just do that without packing the court.
The easiest time to reduce executive power is when your party is in the executive branch to sign the bill.
This has the exact same problem you're complaining my proposal has; it can be undone, quite easily. Probably more easily.
The best case scenario would be to somehow get both parties actually targeting the other's corruption instead of just trying to get the votes needed to be the ones sticking the money in their own pockets.