Account backup options once Facebook backup is gone

I have two MPQ accounts.

I play on both every day, and I spend on both regularly.

For the bulk of my play I use my iPhones, one account on each device.

For some of my play I use my Android (actually Amazon) tablets. This is mostly when I make purchases, as all in-app purchases are less expensive on that platform.

Both my iPhones use the same Apple ID.

Both of my Android devices use the same Google ID.

Q1: What option is there for me to backup my account once Facebook backup has gone that will let me play on both iOS and Android, rather than just one platform?

Q2: What option is there for me to backup my account once Facebook backup has gone that will let me backup both of my accounts, rather than just one?

Q3. What are the issues I and others like me will face if one or other of these things isn't supported?

Note, I'm happy to create a second Google ID if that's what it takes but creating a second Apple ID would be very inconvenient, to say the least.