Yes, I do know there isn't a way. That's the problem with the plugin.
And no, it is necessary because we have users migrating from squarespace to wordpress and we need to have their subscription set with a specific expiration. When the migration is complete we need to give them a subscription that has specific cut off dates.
And don't worry about it, i'm almost done writing it myself; just ridiculously stupid that the plugin doesn't have the ability to do it to begin with.
For all services that use subscriptions, the necessity to modify the subscription needs to be there. Even your guys pointing to the table itself to be edited via phpmyadmin shows that people on your forums have requested this.
There is more to a website than just a 'fresh install' to get started, people sometimes are moving to something that would be more productive and versatile for their needs than they already currently have.