If I might add my input.
I have also been looking for this feature since I started using construct2 but held of requesting since it's a "nice to have". It would be awesome to have my personal CI server be able to build and push to my web servers automatically. Personally I think building one project at a time is fine. IMHO the logic to handle multiple projects at once is better suited in build scripts. Also, I understand there may be a dozen different fields or so but if you build a Visual Studio project with the CLI there can be just as many, or more. ;)
At the enterprise where I work I built a Jenkins Continuous Integration environment for a team that will check out a VS solution and build the code anytime anyone commits. Next it deploys then runs a suite of tests to validate the code; at a high level. If we are able to build C2 from the CLI I'll also be able to configure a unit test framework for my games. That way if I change some events I break something say in level1 the tests will catch it.
Ashley Let me know if something similar to the above for the C2 core interests you. We can talk if so.