I just noticed when checking the campaign home city in the new campaign menu, the game shows you the campaign at the level you unlocked it, not at the level you currently are.
For example, if you finish the first act, Blood, and check the home city from the last scenario, it will show you a home city at around level 10 with all your cards and customization unlocked, but when selecting earlier scenarios I noticed that the city state shown in the campaign menu will be one with lower level, fewer cards and customizations. I’m guessing this was done so the campaigns don’t become too easy when replaying them, but I think you should be allowed to use your full deck if you already finished one campaign.
I don’t remember if this was like this in the original game, so if it was then its all good, but I still think you should be able IF you already finished the campaign or a chapter.