Any smart system can be tricked into confusing friend vs foe, yes its not as simple as entering in the correct username and password into a terminal but that is the simplified version of it. If the mines are smart mines (dont just attack everything that comes near) then it maybe useful to have “dumb” mines too as any smart system can be hijacked (WITH NOTIFACTAIONS!!!) or disabled.
Simple mines would attack friend and foe alike and should be seen negatively by the community at large (similarly to how real mines are seen today). Pirates would not be immune although you may not want to attempt to retreieve the cargo. The fleet laying the mine should always be at the edge of the mine field or the mechanics would force the mine layer to never leave its own mine field. They would also destroy civilian traders as well or force them to avoid that area.
Civilian traders are a thing in all economies today and would open up multiple areas of game play. Traders could be produced and seen as objects or added simply as a background mechanic and never actually seen. If they are seen, they would travel to systems or inhabited planets (traveling to any system at random keeps players and their bases somewhat hidden while also serving their role). This will assist in owning multiple planets in the same system as traders may not leave your solar systems for a few days increasing your income.
By connecting their numbers (either production rate or population, I would suggest the ladder and have that increase or reduce with respect to the trader population) related to the population they originated from (planet or civ) the aformationed mine fields have some worth as is the option to kill the traders if they are picked to be a visible object. This also opens up the concept of spies.
It is unlikely that a spy would board a ship labeled the Nautalus of the player odis in an attempt to gain access to another player’s planets. Instead a spy would book travel on the civilian transports and attempt to take advantage of the system or a player might produce one themselves but would be much smaller than the t1 freighter we have now. It would have a very small scan range (like the diameter of a planet’s orbit small) with engines that dont reach w1.
For this reason, a planet’s owner can check a box to turn away traders. Traders would not enter a planets orbit but a daring spy could attempt to land on the planet at his own peril (with varrying degrees of success including a notifacation that a spy gained access to the planet) and could simply serve as a scout or try to stage a a rebellion among other devious acts. Success rates should depend heavily on race.
Traders would avoid areas with heavy fighting and eventually players might be able to institute tariffs and have a trade war of different varieties although I think this one might be difficult until planets are able to produce goods (ie furs, spices, and diamonds of our present age).
A player can spend currency on security or should that be related to the military presence? Some the former and some the ladder?