I would like there to be a an option in the File menu of Bitcoin-Qt to load a previously exported wallet.dat file. Selecting this option would present the user with a file selection dialog. Once the user selects the file, the wallet should be reloaded with the new wallet to ensure that no previous network connections are reused, for privacy reasons.
This would facilitate much easier switching between wallets. As Bitcoin-Qt has no hierarchical account support, this would help users better segregate funds for their multiple online identities without a lot of accounting and Coin Control use.