Why don’t you want to use PyCall? Or in the case pyjulia (a related package). PyCall works very well, for the calling part. The reason to avoid it, is having to install Python packages, using two package managers, and Python’s just not as good as Julia’s. Those arguments against using together do not seem to apply to pyjulia.
Whatever you do, I would at least prototype first using pyjulia, and see if that’s just not enough. I haven’t looked at the latest option for producing libraries, in PackageCompiler.jl but one issue before was that static apps with it are rather huge, since it actually bundles Julia with the app. I suppose that’s the case with libraries too.