I would like to change my Gmail for Proton Mail. The monthly option for Mail Plus seems reasonable to me. The cost for Unlimited seems a bit too high. I don’t like paying 1 or 2 years in advance.
Proton Support said it is impossible to combine Proton Mail Plus monthly with the Pass Plus for 12 euros/year.
Is there really no possibility?
Indeed currently not. The reason is that currently there cannot be multiple subscriptions on one account. As another commented pointed out, the team is indeed looking to change that in the future, however there is indeed no ETA or further info yet.