Well, 16 inch rims to fit a 205/45/16 will be very very plentiful. You can run a 6.5, 7, or maybe even a 7.5 inch rim on 205 wide tires. The best way to know is to look at the tire manufacturer's recommended rim mounting width. As far as tires, all the tire sizes mentioned exist. It's just a matter of finding them.
www.tirerack.com is always a fun place for me when i look for tires, because they have basically all the informaiton you need. You can even call them and ask for tire weights, if that is also one of your concerns.
Good luck
Maurice