I would go for the swashbuckler instead because it is a single classed hero and the bonuses to hit and attack are great. Furthermore it is a focused PC and you don't have to go through the dual classing stuff.
O btw if you are intent on going the fighter/thief road then you can try to get two strongholds as mentioned in the faq.
The way where you complete the d'arnise keep string but then decline nalias proposal w/o denying her completely. Then come back after you get your thief stronghold and she will be waiting for you on the drawbridge. The you can say that you decided to agree to her offer and get the two strongholds exploit.
