Yes, you can use PackageCompiler for your collection of packages. We are also exploring doing this in the background when you add more packages.

The reason why we can't distribute precompiled .ji files at a package level is because of the way the package resolver works. It depends on the exact versions of dependencies of every package - and even for the same version of an end-user package, there can be slightly different versions of the dependencies installed depending on constraints imposed by other packages.

One major improvement coming in 1.6 is multi-threaded precompilation, and it will leverage all the cores you have.