This isn't exactly a feature request, but it seems like the most appropriate forum anyway. I am really questioning an existing feature instead of suggesting/requesting a new feature.
My question is, why would the average server administrator want to offer programs/scripts like Horde/IMP, SquirrelMail, phpMyAdmin, etc. to be installed per-domain? Instead, they can be installed once globally for the entire server and then made available to all domains automatically. Of course, some scripts need to be available per-domain so they can be customized. But at least in the case of the webmail clients and phpMyAdmin, there is hardly any need to customize them. Also, it is much easier to support and maintain a single instance and a single version rather than multiple copies and different versions spread out in a bunch of domain home directories, not to mention the extra server and backup resources that requires.
In addition, I don't want my clients to have to set up their own webmail clients after their account is created. This should be done for them automatically as part of the hosting package setup. Practically everyone uses webmail, so why not just offer it to them all by default? With SquirrelMail in particular, once it is configured with the[A HRef="http://www.SquirrelMail.org/plugin_view.php?id=47">vlogin plugin</A> (and several others for useful feature additions), it is 100% ready for everyone to use.
As an analogy, I see providing some of these script installers similar to providing a script installer for Usermin, which doesn't make much sense.
Maybe I am missing the point, but I just don't see any strong reason to offer these installers to my clients, and several strong reasons[Strong><Em>not</Em></Strong> to.