Since the thief lacks a two-handed melee weapon granting them 5 weapon slots (excluding the shortbow), how about when you wield the one-handed sword on it’s own you get five weapon slots and would be played like a European Duelist!
These skills would be the ones we have now in slot 1 and 2, but 3, 4 and 5 would focus on parries, counters and cripples!
At least this would be helluva lot better than the current alone sword slot 3 skill(stab?).
Just an idea