Can I erase a missing device to iCloud after removing it from My Devices?
I'm afraid since the device is removed from Find my iPhone app you can no longer make changes from iCloud.com. If you would be able to start the device again - sometimes you don't even need to go all the way as fully booted system - it will reappear in the Find my iPhone app.

I work at a retail chain as a service agent and have seen this many times. Customers wanting to leave their phone for repair/replacement, have removed the unit from iCloud.com but not erased it - simply starting it will reactivate the Find my iPhone and remote erase is available again.

Hope you get any way to start the device - even if it's not a fully booted system.