"Do you think it's reasonable to include account resurrection / merging into one of the paid plans?"
No. I believe that the paid subscription plan will be unable to cover the costs of such feature. It's an unnecessarily expensive action, when Imgflip has a message that explicitly states that when deleting an account, you can't get the account back. People have to read the said message before deleting their account. Keeping this message and not implementing this feature at all will save up a lot of costs.
In other words, It's financially unreasonable to implement this feature, even under a paid plan.