Also, once you've done all this you can download APKs from Google Play Store without needing a burner phone. They've had extensions that do this for some time. Might as well just do it from the computer and or use an alternative app store.
If you really don't want someone to sign in to Google services, then there are ROMs made specifically for that. Have them use CardDav and CalDav. Use email with IMAP, etc. The route you've chose seems way too convoluted for no purpose other than the illusion that you're somehow unidentifiable.