I think most people browsing the web today should prefer https where
it's available, so default installations of iceweasel should have
https-everywhere included.

It would be great to add:

 Recommends: xul-ext-https-everywhere

to the iceweasel package.  If this is too strong for some reason,
please at least add it as a Suggests (it's more important than
mozplugger, which is already Suggests).

Regards,