I feel this suggestion would make the game feel to casual and cause the developers alot of head aches to implement. Regardless of that effect, the game used to force players to buy goods with their own earned money, to be able to have trader goods now for free is more then fair In my opinion. If you find your trade route filled with too many raiders I suggest you sail as your own escort ship or ask/hire others to come with you. Or you can join a faction with more safer trade routes.
ps. The land-merchants giving you their goods for you to transport do not even come after you if you loose thier goods. In real life, merchant companies would be sued if they lost the goods of their owners!?