Based on many people I've spoken to, it doesn't appear that this is possible. BTC fees are based on transaction size and nothing else. The client lets you pick your fee per kb. The issue is you don't know how many kb you're using (or bytes) until after it's been created. Look at the Bitcoin Core code yourself for further verification, since you don't want to believe anyone else.
Are you saying that you believe that there is no way for you to manually set your fee when you send bitcoin? Would you like to wager on this?
Considering we do manually set the fees and you are unwilling to look at the Bitcoin source code for confirmation of how it works, here's a more broken down version (in pure English):