The down apron idea was evolving (read about down apron - entry1, entry2), I was thinking of a system with detachable sleeves and a detachable back piece. However that's overly complicated for an experimental piece: too many unknowns at the same time often lead to frustration and either abandoned project or compromised solutions and changes that are made too late, which is frustrating as well. I like to have 95-100% of a new design clearly outlined in my head before even cutting pattern. So I isolated an idea of detachable back panel and started working on it. On the way it have merged with an idea of a wind anorak.
Here is the first prototype:
As you can see on photos and video there is two closure points, at the neck and at the waist, both use mechano-magnetic buckles that are easy to close behind your back - they align themselves when in close proximity and snap closed. Though I like them a lot, they are not a perfect solution for such a lightweight garment, they add weight considerably and then they also pull down, upsetting the gentle geometry of the garment.
Back panel is attached with two 10" zippers along the back of the sleeve edge. From this video demonstartion you can see that 10" is not enough, even if you are rather flexible:
(in the end of the video I forgot to tuck the back piece under the waist belt, I was too happy that I have managed to zip the back on, without taking the anorak off, but you can see the final configuration on photo above)
There is a lot of other little aspects to work on, but for the first prototype of a weird idea I am satisfied.