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.