As a quick addendum, you would be able to have a different custom screen not just per character/variant, but also per saved build slot. This is again to take advantage of a lot of options so you don't feel you're wasting things you've unlocked.
On the Reddit, GlobalAd5132 posted an idea for the next game that could add even more to your customizations, and I felt I had to share it. Currently when you are vanquished you hear that bell sound as the punchers punch, it's about the same in all 3 games, but what if you customize it?
Obviously one has to be careful of what sounds are used but I was thinking of stuff like; Crazy Dave/Dr. Zomboss voice lines, 'Brainz', and other classic PvZ sounds as well as various bells, whistles, and so on.