help with storage options on Apple One family plan

My partner and I each have separate 200GB iCloud accounts (so that's 200GB for me and 200GB for her). We were looking at getting an Apple One Family Plan to share, but I've read that if we switch over, we will then have to share a 200GB iCloud storage account.

Our phone backups each take up about 110-120GB on our iCloud accounts, so that would not be enough space to keep both of our phones backed up. I know that the next step up is 2TB of shared storage, but that's insane overkill for us. I doubt we'll ever use more than about 300gb of iCloud storage combined.

Is there an option with the Apple One Family Plan to add another 200GB of storage so that we could keep a similar setup (400GB total), or is the only other option to pay almost double for the (very unnecessary for us) 2TB plan?

Thanks!