At this point it's still a solution looking for a problem.

Seriously.

MSYS, FBB and several other radio-based BBS systems will do all of what
you described. With MSYS, you have the ability to serve content from
callbook CDs or other mounted media - so a "Sale" or "Mods" directory
could be readily served up.

"...It would be a network that only amatuer would be able to use
(like Echolink)..."

Who is going to develop this app? Or is there one currently available?
How do you verify that -only amateur radio operators- can access the
I-net sites? IOW, what does your security model look like? Which parts
of the path are to be encrypted (so as to protect login credentials,
for example) and by what means will the encryption be accomplished?

I know a bit about this area, and can unequivocally say thay security
in such a system would not be trivial. Nor would the potential for
abuse, especially if there is any type of connection to it that can
directly be reached through the Internet. Choose your operating system
(platform) unwisely and the headaches become even bigger.