Hi,
sometimes i face the situation of trying to download a torrent which contain a big sized file almost too late, as there is only 1 seeder left and this one don't care too much about those who are leeching from him (the kind of people who open the client only for few minutes to download something then come back after days or weeks) . Let's say the more important part of the file for me is not the beginning nor the end but something in the middle , in this case neither normal or sequential modes are useful, because in both cases i might end with a dead torrent after having 40% or more downloaded but still without getting the part i want, that's why i wish you can add an option to prioritize torrent pieces from number X to number Y.

That's already a thing. Select multiple files > right-click > priority > ordered

You are confusing torrent files with torrent pieces, thanks for trying to help anyway.

Not sure why would you need the middle of unfinished file but try Vuze. You can select force piece in right click in piece map tab, hope this helps. I think Tixati COULD put visability and management options for pieces tab, but this feature is not in high demand so it might take a while.