My deployable bin for scala projects currently hits about 50MB, and almost 40MB of that is jar's that are not likely to change between deployments (scala-lang and aws). Is there a way to externalize them from the packaging, so that every build doesn't have to include them?
You can write your own deploy task. Use this code (https://stackoverflow.com/a/9519397/1809978) to customize deploy folder and choose the only jars you need (by marking them using attribute like "org.package" % "artifact" % "1.0" % "external"). And repeat same for internal folder.
P.S. About referenced code: it's better to use sbt.IO for working with files.