But rejected.
Our monetization plan was to use consumable In App Purchases for unlocking certain features. We knew that will most likely be not approved by Apple, since when a user "unlocks" something, it has to be made available forever, so a non-consumable IAP has to be used.
The idea was that we have platform-specific accounts, so a person might want to create several accounts, which is not possible with non-consumables. So we tried our luck with consumables.
Surely enough, we got rejected. So we reworked our logic a little to make use of non-consumables like this:
It's not perfect: users will be able to upgrade only one account, but that's what the vast majority of users will do anyway.
We submitted again and waiting on Apple's answer.
Premature optimization and premature thinking of all scenarios is bad. You might end up not needing any of it.