If yes, how can this be done?
The reason being that I want to spend the balance, but I don't want to set the wallet up again and sync it as this takes a while. It's just a time saver I'm hoping for.
It's currently not possible.
There is no function to do so in the current software. I did a test where I replaced the .keys file of the view-wallet with the .keys file of its full-wallet counterpart but that resulted in an error, as expected.
As per Jolly Mort's comment, this is currently not possible.