Duskblade or warmage sounds like the best options, but there are others.
If you want to be a support character, the marshal should be considered. Being pidgeon-holed into a race with a Cha penalty sucks, but the marshal is stunning when used properly even if that is taken into account.
A swashbuckler/duelist isn't a horrible idea, but it isn't an incredibly effective one either. Still, it would play to your race's strengths.
Is spellthief on the table? I know your DM doesn't want you to be able to know powerful magic, but did he ever say you couldn't steal it?
And the warblade plays much differently from the sword sage. I've seen them both in play. They have different sets of maneuvers. It's kind of like the difference between playing a wizard and a sorcerer, both have their strengths and weaknesses even though they kind of do the same thing.