High sea towing ships would be great addons, beside the fact they are often nice and manouverable ships, they give lots of possibilities in terms of possible missions inside Ship Sim.
I have in mind the new Abeille Bourbon, which operates in France, in the North Sea, one of the busiest and most dangerous sea ways :
80m long, 16,5m wide, 6m draft
fully loaded highest speed (wind 2bft) : 19,9 knots
fully loaded highest speed (facing wind 7bft and heavy sea) : 16,5 knots
4 main engines of 4000 kw each (total 16.000 kw / 21.000 HP)
bow thrusters : 2 x 883 kW
aft thruster : 2 x 515 kW
towing capacities : two winches (200 tons pulling ability each)
And so on ... That's a really beautiful ship !