I think one valid reason for creating a new distribution is if you have some architectural ideas you want to experiment with. A fresh distro may be easier then

I think one valid reason for creating a new distribution is if you have some architectural ideas you want to experiment with. A fresh distro may be easier then trying to modify an existing one, due to fewer cascading effects of your changes. But in that case, I would start with something like Linux from Scratch and go from there. Ideas that I've personally wanted to work on involve system initialization procedures (this was before Upstart came around), packaging tools, overall package layouts, etc. But if I did that I probably wouldn't promote the distro, since it would probably be useless to anyone else but those working on the specific projects.