Well, sailing with real sailships, I will play a collision like it is...no different between friendly and enemy...in both cases you will get the damage, and, if an enemy ship, more action (rifle fire and so on) will follow.
Thinking about only one little houserule: ramming in 90 degrees or face to face is special: think in that case the rigg (mast and sails) will come down and makes a heavy damage. That is the imported reason not to do it. There I will give special damage points.