I need to create CRX file on the fly. It's for my CMS backend, so it will be just for authenticated users who can install CMS backend as webapp and offer some more privileges to the web app. The problem is, that the backend is used for many domains so creating CRX file for each of them is quite a work. So I figured that it would be easier to just create CRX file on demand which would be generated by PHP using its own domain and probably custom icon.
Looks like I have found exactly what I was looking for. Chrome team has made this option to create CRX-less web apps, just by using simple manifest file.
Much easier to create own webapp and publish it on website for installation. And it also solves my problem when I have many websites with a lot of domains and I don't have to create custom CRX file for each domain. I just create small PHP script which creates manifest files on the fly for each domain.