Be able to use regular expressions to define shortcuts. Also provide the ability to define capture groups and pass the capture groups to the snippet as form values.
For example:
/(.+)/ would match /a/, /xyz/ and /foo/
Potentially named capture groups could be supported or a form variable like captures could be injected as a list into the snippet.
This would be a significant upgrade in my opinion. I'm surprised it hasn't received more upvotes.
Keyboard Maestro can do this, but the macro interface is a little work to set up, but I used it to create patterns for verb tenses and plural forms. It really cuts down on snippet repetition since I use text expansion apps for smaller snippets regularly.