Never had issues with windows sealing, never seen any with rust, and I looked at a fair few before buying, interior plastics have not faded at all and mine is approaching 8 years old, lift bolts are only issues with pre-facelifts and maf sensor issues are usually only when people go for custom intakes..... so most of your points are invalid! Any car in the world needs (General maintenance to keep it at its best) and car enthusiasts look after their cars so you will never really come across any major issues. The only point that is valid on your list is the brakes being poor, but its not too difficult to sort really.
And I think the rust comment should definitely be on your gen 6 list,
As said mate, you should go and drive some and see what you think for yourself, only you will know if you will like it. I like both generations of the celica, and I would happily own either, but I just prefer a newer car.