You should

a) let DOL/DOH undertake the Supply/Provisioning missions for other nations at an improved extra seal rate and then allow access to the other nation's items

b) allow DOW/DOM to assist with any caravan escort, again for an improved seal rate that can be used in the nation assisted (might actually find someone to do caravans with then...)

c) or from another angle, let us sabotage and rob other nation's caravan's and walk off with their gear =o

or d) simply allow purchasing from other nations at a more expensive rate like buying other nation gear in FF11