I think going forward, most EV battery warranty would like be pro-rated so that salvaged limited range battery can be used for warranty claims. Also manufacturers would offer trade in or upgrade program to let owners trade in a limited range battery for a newer longer range one, and the limited range batteries would be sold to those needed to extend their beaters' life.Maybe not aftermarket, but reconditioned used batteries definitely. It’s my understanding that Tesla installs reconditioned batteries as replacements when there’s a battery failure covered under warranty.
The only problem is there are no standard on size and type, so it is very limited on what can be swapped into what.