Make Ubuntu capable of mounting the supporting media read-write and keep a persistence fs image in that same media

There are many howtos explaining how to put Ubuntu in a flash drive. All of those that include persistence call for partitioning the drive in two. The main reason behind this is the read-only mount of the base partition which is something inherited from the fact that Ubuntu "live" is mainly targetted to a cd. This read-only restriction seems simple to overcome. I have done it for my own sake but I think adapting what I did to something decent enough to release would not take much effort. Since it is quite a delicate part of the system I wouldn't dare think it can be applied as it is and most importantly, with so little testing, so I thought I would just show it here and let it find its way if someone is interested.
Please look at my initial post in the forum (spec url)