A GnuPanel appliance might be a neat idea. It's not currently on our todo list because we're not familiar with the help of the community anything is possible. If you want to get involved in appliance development, take a look at TKLPatch. You don't have to be a programmer to get involved.

Regarding combinations or megapack appliances my personal interest for example is to work on features/appliances which help the largest number of users. There are an endless number of possible combinations and since you don't have an infinite amount of time you have to decide what to best spend your time on. Also combining too many applications into one appliance tends to increase complexity and decrease security, but don't let stop you from developing your own megapack appliance if you are interested.