An unofficial/fan-made ship skin editor for WipEout Pulse is available here:

Screenshot from 2021-03-24 11-39-24.png

https://thp.io/2021/shipedit/

Windows builds are available on itch.io: https://thp.itch.io/shipedit
The source code is available on Github: https://github.com/thp/wipeout-pulse-shipedit

Thanks to everyone for sending in their archived ship skins, which helped figure out the savegame file format.