Make the offensive ops/attacks delay 7-10 days long and put a limit on the maximum distance exploration ships can travel (~5-10 units -- I would suggest setting it to the distance from the most isolated system to its nearest system, basically the longest closest system distance in the map). My first thought was to have the distance limit only be for the nearest family occupied system and also have the requirement that all family occupied systems be full to explore new ones, but this is probably a million times easier to implement.

Getting to choke points where single systems have few close by systems would become very important and would add a lot to making the map layout interesting. It makes more sense to me because it would be more organic growth and could be explained by reasons like supply chains. It would be interesting to see strategies related to this since it would be similar to the longest road achievement in Catan with strategic blocking of other fams' advancements. Exploring towards one family would be at the loss of not moving towards other families. It would also stop the hyper escalation of conflict that usually happens - explore a little around HS and then send explores to the halfway point between HS and another fam to see what happens.

If we wanted to go even further down the 4X game style route, you could have to fund a certain set amount of gc into a family shared research category (5M gc?) to unlock the ability to build military units instead of having the long timer before offensive attacks/ops. This would add uncertainty and give the first family or two to save and invest in this a time buffer before anyone can fight back at the expense of losing steam towards their economic development. Families who completely ignore this would be pretty screwed if they get surprise attacked with no savings. I think this might also diminish the major disadvantage the first few families who start fighting face since everyone else blows past them eco wise since its always a good idea to avoid any conflict early on. With this it would be pretty risky to not invest in military after others start fighting. I think these ideas are interesting and would be fun but I'd be happy if the cost to launch attacks and send explores scaled with distance exponentially instead of linearly. There is currently no downside other than time to going super long range with explores/attacks since 100*distance gc is insignificant.