No, it should not. But it can suggest using it (same syntax as require, but you use "suggest" instead of "require".
Why? Because there can be alternatives to this Installer or some people dont want to use an installer for them at all. As a module publisher you only decide the type of your package. It is the responsibility of the package user to decide what installer or plugin he uses to handle this package type. Also by require the installer, you can produce version conflicts, as people could start require specific versions of the Installer. Which makes absolutely no sense for a module.
currently No. As we need special configs this makes things a lot more complicated then installing on project level.
Yes, we got a big contribution for a special install method regarding the magento/core.
Sadly the transfare into this installer project was more complicated then expected and it occured some issues.
As the Issues were not resolveable, and there were not enoug tests for this part, we decided to remove this feature.
If you want to use it, we suggest to use the bragento-composer-installer.