Currently, the only sails in the game are the classic square sails that date from the Roman period. You should NOT be able to sail against the wind at all with these, but it's a game, and not meant to reflect reality.
However, how about adding some variant sail configurations that would give advantages and disadvantages (Balanced) to the ships that use them.
variation 1: Lateen Sail. This would replace the sails on one mast on the ship with a triangular Lateen sail, a sail designed to tack against the wind. Each mast can be left with a square sail or fitted with a Lateen Sail. Advantages: Can go "Full billow" against the wind, so long as the ship is at least 10 degrees off from "Truly against the wind" and the sail is all the way on the side opposite the wind. Disadvantages: Though it increases "into the wind" speed with full billow capability, it is NOT as good when sailing with the wind, slowing the ship's maximum speed with the wind. Also, does NOT have a horizontal spar you can stand on.
Variant 2: Spinnaker Sail. This Sail has no spar at all, it is attached to the mast and held by ropes alone. Advantages: Has a much wider "Full billow" angle, being nearly 90 degrees, so long as the ship is sailing in the 180 degree arc with the wind. This means it needs much less attention to maintain speed with the wind, and also is a bit more efficient with the wind than a normal square sail, providing a speed boost (with the wind, A Sloop would use brig speeds, a brig would use Galleon speed, and a Galleon goes even faster than it normally would. It can ONLY go on the forward mast, replacing the square sail on that mast. Disadvantages: No Spar to stand on, Against the wind, it is very slow, adding about as much speed as a square sail that is half-furled.
