Newsletter => create profile field checkbox "subscribe to newsletter" and show it on the privacy page..
Addon xxx => create profile field checkbox "show my points to guests"
Addon Foo => create profile field "hidden for user" (only settable in acp & via php code)
ATM we would need to create a extra column in the user (or other table), extend the user datawriter, add output to the template(if needed) , etc...
If we could use profile fields for this, this would IMO make many things much easier
(I hope you know what i mean )