My solution to supply problem

To avoid exploiting in supply production, my suggestion is that supply production became allowed only on planets with suppy depot and only one supply depot became allowed per system.

so, if you need a big fleet to go to war, you need to pay an extra for the supplies, like in real world wars.

Just my 2 cents.

That´s different, by making 10 supply depots in a system you are sacrificing space that you could use for research or mining. But like in real life, you could have the option to use your industrial (construction) capacity to support an atacking force by building supplies on planets.

Think about it, it cant be exploited, if you have a planet with 6k insdustrial cap, and it makes 6k supplies every turn, it is already a lot more playable for large fleets, but not enough to make supply line a small detail again (like in SEIV,where you simply need a single supply built in emergency).