It might be useful to also offer the ocaml-platform installer as an opam package (bootstrapping problems aside, of course it is useful to have an installer that does not depend on opam).
It looks like the ocaml-platform tool would be beneficial even if you already have opam and a development environment, as it seems to offer a convenient way to share various developer tools between multiple opam switches (and it could perhaps build and install itself as one of such tools, so it can be conveniently be kept up to date).
It might also be interesting to keep an eye on providing a binary built using the APE format (see APE Loader) which would be a single binary that would run on Linux/Mac OS/Windows/etc. See [ANN] Esperanto, when OCaml meets Cosmopolitan, unfortunately its support for threads.cmxa is not yet complete at the moment, but seems to be a promising alternative for the future, especially with the APE loader, which doesn’t require self-modifying executables anymore.
But of course the best would be to get this installer packaged for distros (and part of distros by default like opam is), and perhaps working with a package maintainer to see what it would take for ocaml-platform to be packagable (not requiring to download binaries off the internet, but building everything from source would probably be one).