I've got a project going on, far away from complete, a stand alone audio mixer/effects processor. I plan to eventually, have all of my effects in stand alone program as VST, AU, and maybe TDM plugins.
I would like to be able to batch convert all the files in a project using an external sample rate converter. If not your choice of external converter, then just a specific program, R8 "brain free", or "R8 brain" pro, by Voxengo.
The second thing I would like to be able to do, is launch "Reaper", from within a project in my program, and have the files in a project, opened in reaper, and all of my effects plugins added with specific settings.
Is this even possible to do?
It depends on what level of automation interface the other programs offer. This could range from taking command line parameters to perform certain actions, to offering a sophisticated automation interface through a mechanism such as COM or OLE automation. It's a matter of checking what is offered by the software you plan to run from your own program.
The reaper documentation suggests it has quite a good API for automation purposes.