FastR can actually run all tests of the development version of dplyr with a simple patch. We're working on removing the need for that patch altogether.

data.table is a different beast and we will probably provide and maintain patched version for FastR. They do things like casting data of internal R structure to byte array and then memcopy it to another R structure. This is very tricky to emulate if your data structures actually live on Java side and you're handing out only some handles to the native code.