login & pwd for standalones ?

[jbv]

Folks,

One of my clients wants a webapp with a large
set of functions, and he's gonna distribute them
to his colleagues, but needs to enable / disable
certains functions, differently for each user.
He also wants a login & pwd for each user (that
will be entered at start up) and possibly limit the
use of an app in time (3 months for instance).

Of course, I can do that with variables, and build
as many different standalones as different users.

But I was wondering if there was a more general
(and more efficient) way to do that... especially
because my client isn't going to call me everytime
he needs a new copy with specific login + pwd +
time limit, and also because he isn't going to build
standalones by himself...

Thanks,
JB