SEM Actions - REST API - Execute Program

We rely on SEM sending email for external alerting, including auto-generating incidents. In the not-too-distant future, support for auto-generating incidents via email will be going away, so I need to find another way. Calling a REST API from SEM would be the preferred method but that isn't an available action.

Any reasons why executing an API call is not an available action? Is that planned as a feature in the future? 

Similarly, if I could run an external program, analogous to logging to file, I could have that program make the call, but that's not a SEM option either. Same questions as above.

Anyone in a similar situation cobble together a solution? I have a couple thoughts on how to accomplish this but wondering if others have dealt with the same issue.