Pay attention - we are called miniBB. For being miniBB, we have eliminated some features which are needed once per life. Installation script would take the whole size of miniBB. We don't understand what's so difficult in opening file in notepad, configuring it and then uploading back to server. Or are you simply too lazy? :) If you are going to install script for public use, you should know its working principles. Web is full of lamers garbage, sorry... we are not ready for it.
Just a philosophy :) It would be a nice feature, but the more nice feature is to be secure, sorry.