Home Network Sharing/Syncing

My family asked me to help consolidate their music/movie library. They had some requirements first:

1) They would like 100% of the music/movies they own on one central external harddrive that is connected to a computer that is available to their home network.

2) They would like it to share between the 1/2 apple tvs, 1 central computer, 4 personal computers, 4 ipads, and 2 iphones....

3) They would not like the media to automatically import the content to their own computer, to have the ability to save room on the hard drive (and if it is available locally over wifi) why would it be necessary for it to be imported to the computer.

4) They would like to have their own viewing library though on their iOS devices, but have it just streaming over the wifi, to personalize it for themselves.

5) They would like the option to sync the content to their ipad, or iphones if they so chose to, so when they leave they can listen to what they have.

I know some of this is possible, but would like to know if all of these are... I am also not sure I am wording it correctly, and if there any questions, please ask. Thank you so much in advance.