Has anyone come up with a tool that would allow the transplanting of an address into a different wallet.dat?

Let's say I have an extremely bloated wallet.dat that's 300mb with thousands of addresses that are no longer needed, except one of them.

Obviously it'd be nice to start a fresh wallet but that one individual address that I need has been published and may receive income in the future.

How would you work around this at present (and ideas for the future)?