Sensor barges remove the first X from 4X almost completely making the early game boring.
You can get 20-30 sensor range barge on turn 2.
Mechanic like that would be considered completely broken and would get laughed out if it was in a game like civilization IV/V or any other 4X game really. Is GalCiv really that different design wise from other 4x games that it makes units with insane vision radius not completely broken and OP? Why do all other games that still manage to have deep and complex unit customization systems do now allow you to have retarded sensor ranges? Can you name one other game where it is possible?
It makes the +sensor racial trait and sensors on starbases worthless. Once you get sensor miniaturization and tier 3 sensors you can get a 60-70 sensor ranges ship which is basically whole map making high tier sensor techs are also worthless. Why are those things in the game at all?
How the hell is that not broken?
"Well then don't use them"
It's not so simple. Limiting yourself to just one sensor per ship is pretty harsh. So how many exactly should you use before it becomes broken? 2? 3? 5? 10?
It's a slippery slope and once you decide you want a sensor ship for scouting you want to make it the most efficient you can because that's a sound strategical decision. It should be developer not the player that decides the point where a strategy is too strong.
People posted lots of solutions but they require significant changes to the system and/or aren't very intuitive.
The best solution would be to just make the sensor modules limited to one per ship. There are already 1/ship limited modules so it's just adding one line in 5 places in a .xml file.
The old modules aren't obsolete so you can put multiple sensors but each next one will be the older tech one.
It's a simple and effective solution which basically gives diminishing returns on sensors while still allowing to stack them somewhat.
So on tech 0 you have just one module with +2 range
One you get interstellar engineering you get another module which gives +3. You can stack it with the old one for +5 total.
After you get next sensor tech you can add another module for +9 total.
Each new tech level brings a significant increase in sensor range so researching them is actually desirable now. You can't get all the sensor range you need by just grabbing interstellar engineering and putting 10 sensors on a cargo.
It makes the sensor range on ships comparable to the one you can get on starbases making them viable choice of upgrade. The racial trait also becomes very useful for that early game bonus when it counts the most.
It limits the sensors early game and forces you to actually move and explore with ships like you should and like you do in every other game.
Later in the game you can still get 20-30 sensor range which means you can get very effective sensor support ships for your fleets without the need for too many of them.