For anyone still following this thread, I have made a much better new version of DisplaySpacesManager that is able to add and delete spaces. It attempts to restore the configuration you saved, including app bindings and desktop backgrounds.
I have been using it ok for a few days, I think it’s ready to be tested externally.
http://downloads.binaryage.com/DisplaySpacesManager-1.1.0.zip
It will only work with this pre-release version of TotalSpaces2, which needs to be installed first:
http://downloads.binaryage.com/TotalSpaces2-2.2.18.dmg
Any previously stored configurations from earlier versions won’t work as the save format is different.
Tested with Yosemite only. And reminder: you need to have a license for TotalSpaces2 for this to work at all (trial version won’t work).