In Android, view previously opened web page when offline
The Sleipnir browser for Android has an option for making all tabs remain loaded even when the phone is offline. No need to specifically save a tab or do anything special to make your tabs available when you're offline. I'm not sure about the details, but it seems to fit your needs. The Mac/Windows versions of Sleipnir has much cooler features than the Android version, but it is still worth a try.