You can also use breaded eggplant in the sandwich.
Eggplant, on it's own doesn't freeze well, but if you bread it first, then it will freeze well, for frying later (in either parmesan or for sandwiches).
I've also used eggplant in spaghetti sauce instead of meat, and you can freeze the sauce okay.
I'm glad you are enjoying all the eggplant. It is actually one of my favorite foods. Story time- the first time I had eggplant, I liked it so much, I took a flat of eggs and went in the yard and "planted" them so I could have more. My father was NOT happy, my mother laughed - it made sense in a childs mind.
"Make it your ambition to lead a quiet life, to mind your own business, and to work with your hands, just as we told you, so that your daily life may win the respect of outsiders and so that you will not be dependent on anybody."