As mentioned earlier, the JQM team has updated the collapsible design, so that it is now possible for these to have a background or no background. This is a fantastic news for this type of application, as I can really easily display collapsible content with the look that is optimal for the chosen content. This is the major addition to the v1.0 RC1 as described in the release notes.
I’ve also had a discussion with the JQM team regarding the possible loss of the bottom rounded corner on the last collapsible header when expanded, see github issue 2584. This will not be implemented but I could still do it if the iWestminster team felt that it was necessary.