Yes, Marvin for Android would be great. I love Moon+ Reader Pro, but it's not quite on Marvin's level. I'd rate Marvin 3.5 stars, Moon+ Reader Pro 3 stars, and all other e-readers 2 stars or fewer. So, the overall situation is looking pretty bleak.
Given that Marvin for iOS itself hasn't really been developed in recent months/years, either, and must be considered an unfinished product at this stage (not quite "abandonware", I hope – that would devastate me), the idea of a Marvin for Android appears to be pure fantasy, unfortunately.