I wasn't able to reproduce this. I tried with a new file called deleteme-ds.xml. Deleted it through the ProfileService and recopied a deleteme-ds.xml into the deploy directory and it booted up.
My next test is to take that copied deleteme-ds.xml and change its jndi-name in the file and reboot to see if that reproduces the problem
Nope, that didn't reproduce the problem. If I get it again and remember something specific that can make it reproducible, I will post it.
Well, while I wasn't able to reproduce the error with other datasources. I was able to fix the problem, by deleting the deleteme-ds.xml.attachments file from the server\default\attachments\ServiceXSLDeployer directory.
So that file must have still had the jndi-name as DefaultDS (hence the conflicyt with the Hypersonic datasource), and was not updated when I made the change to the actual deleteme-ds.xml.