Make cargos lose a % of value on lost battles, because right now there is no real risk in trading, there's only the matter of how long it takes. Maybe make it lose only profit value so player can still always get the deposit back, or after profit is decreased to 0 deposit value could start decreasing too.
Example, assuming a 10% of profit value lost on each lost battle:
Player picks up 500/100 cargo paying 500 gold. On his way to delivery target, he loses 3 battles, so he loses 3x10% of 100 profit, so 30, and his cargo is now 500/70. He delivers the cargo and receives 570 gold, making only 70 profit instead of 100.
Another example, still 10% of profit value lost, but now with possibility to lose deposit value:
Player picks up 2000/200 cargo paying 2000 gold as deposit. On his way to delivery target he loses a total of 12 battles, so he loses 120% of profit value, 200*120%=240. Cargo's profit is now 0, and an additional 40 is subtracted from the deposit value, and the cargo is now 1960/0 (or maybe it could show as 2000/-40 ? ). Player delivers the cargo and receives 1960 gold, losing 40 gold in the process.
Of course all the numbers are subject to change, could be 5, 15 or 20 %, instead of only the profit value the % lost could be of deposit or entire value.
Example, assuming a 10% of profit value lost on each lost battle:
Player picks up 500/100 cargo paying 500 gold. On his way to delivery target, he loses 3 battles, so he loses 3x10% of 100 profit, so 30, and his cargo is now 500/70. He delivers the cargo and receives 570 gold, making only 70 profit instead of 100.
Another example, still 10% of profit value lost, but now with possibility to lose deposit value:
Player picks up 2000/200 cargo paying 2000 gold as deposit. On his way to delivery target he loses a total of 12 battles, so he loses 120% of profit value, 200*120%=240. Cargo's profit is now 0, and an additional 40 is subtracted from the deposit value, and the cargo is now 1960/0 (or maybe it could show as 2000/-40 ? ). Player delivers the cargo and receives 1960 gold, losing 40 gold in the process.
Of course all the numbers are subject to change, could be 5, 15 or 20 %, instead of only the profit value the % lost could be of deposit or entire value.