How
could I do a system wide install of modules with OPAM? In linux, in this case.

It looks like this is not preconfigured, but should be not too hard:

Change the environment variables to your system install dir, put them into /etc/profile.d/ or what is convenient.

Or do you think this is only for development, and deployment will be binary?

I am especially interested in scripting with ocaml.

/Str.