I believe there should be some form of interstellar banks, with branches in different size stations - for example 'gravity' stations have full banking facilities. the outpost station could just have a simple facility, maybe just a balance function or some such, possibly a deposit function. This would allow you to put money into the banks and preserve it through ship destruction. Purchasing of ships or equipment could have a buy via bank function allowing you to keep a set amount onboard your ship (open to loss etc) and pay for 'enhancements' using money saved in the bank.