frequently on my projects I have to add some layers at the middle of the development. It's easy when you are working with 2~5 layouts, but when you are at your 20th layout (about 15th or 17th stage) and you NEED that awesome feature that claims for a new layer things get complicated.
I know I can create whatever is in that layer by events (that's how I do now), but if the layer don't exist you'll need to create it. Adding and setting a new layer for each layout is an ungrateful task...
It would be nice to have one or more Master Layouts. If I needed a change that applies to some layouts I would just change my master layout and voil�! All layouts are based on that master layout would change. Be in the order of the layers, creating a new one or the exclusion of an old layer.
Is it hard to do? Would a plugin be able to do that? If it is, can some of our plugin devs do that? If it isn't, can Ashley put this on the list of future features?