In general, it is possible to make a staking wallet for Android. But you will need to keep full blockchain on your Android device.
Well with the modern cell phones storage capacities that wont't be a huge problem. Especially for younger blockchains like Digigreen

I agree. But there is still a problem with battery capacity - staking wallet is using a lot of power.
Once digigreen is ready to go, how will the swap from dopecoin to digigreen be handled?
There won't be swap, at least for now. It is just rebranding, blockchain remains the same.