In terms of size, there isn't much you can do about that. It's kinda hard to store large amounts of graphics without taking up a lot of space. However, depending on the tablet you use, it may have expandable memory in the form of a SD or Micro SD card slot. You may be able to transfer the files to an SD card (not too expensive, maybe $15 for a 32GB one). It will run *slightly* slower, but you will have more space on your device. Alternatively, you could transfer pictures, videos, and other media to the SD card rather than the game if you want to keep the game on your device so that you can eject the SD card without affecting the game.
In terms of battery consumption, you can always turn down brightness, turn off Bluetooth, and reduce applications running in the background. Turn off animations; they take more processing to run.
It goes back to one of the more unfortunate aspects of technology: eventually you will have to upgrade to keep up; kind of the Red Queen theory, but tech rather than evolution.
[EDIT] I suppose that the only true optimization Inno could make would be to release a version of the game without any animations, limiting it just to the static graphics, but that would be a lot of work on their part for no gain whatsoever. If you are good at editing files and know what you are doing, then you could delete the files for animations you don't need or want. There is a chance that would invalidate the game, but it could be done. It is probably against game rules and the ToS, but it isn't impossible to do.
