It supports a lot of the stuff you are looking for as it regards communicating with the underlying process.

Unfortunately, I doesn't support terminating the controling program and reconnecting the underlying process with the terminal.

In fact, I don't know of anything that does that. Expect-the-language (as opposed to Expect-the-module) has a command that stops the program looking at the input, and just makes sure the data passes from one to the other and back unimpeded, but even then you still have both your Expect script and the whole Expect interpreter still loaded in memory.