They should be designed in a way that they are NOT fortresses, that's what Defence/Administration Stations are for.
And I agree that they shouldn't be bullet sponges either, just low HP structures that need allot of resources to build so they need to be strategically placed where enemy ships would have difficulty reaching them.
Stations can be built to ridiculous sizes. The probelm with Jump modules is, that nothing prevents players to add hundreds of defence modules on their stations in addition to the jump modules. Any ship that would dare getting close to such a thing would be vaporised. There is no system in place currently, that makes this and either/or choice. At least to my knowledge. You can have both at the same time. That's why any jump beacon technology should never ever be a station module of any kind. Regardless if the modules themselves can be destroyed easily.
also they need to be limited so that the only beacons that you can use would have to belong to allies and your own.
That was always the case in AP and I think FL. You had to have good reputation with the factions involved if you wanted to use them. Granted, there were more reputation levels than in X4, and maybe jumb beacon access was a bit too low level, but it was still a thing.
That you shouldn't be able to just teleport into the Heart of Xenon Space with a mega fleet and take out their Shipyards/Wharfs?
AP balanced beacons quite well. You couldn't buy them, and you couldn't build them (in vanilla). The only way to get them was hunting down the Rapid response fleet ships (which we may need in X4 too anyway). And even then you only got maybe one of those if you successfully boarded them. In X3, that meant a lot of money and time investment for the player, as it was not easy to board ships, unlike in X4 now.
Additionally, the AI in X3 loved to actually target and destroy deployables of any kind. Even the mosic basic drone could destroy a beacon easily. So planting down a beacon in hostile space meant you most likely would lose it. And losing a beacon in X3 AP was much more devastating than anything else. There was no replacement for them, unless you wanted to go through the tedious boarding process again (which was also heavily RNG based).
Bare in Mind also that each Jump Module can house only 1 Large Ship (Agree with Mr. Who that only large ships should have access to it.).
So if there is 1 Module? Then it is 1 Large Ship at a time so it can't be abused simply because time is a MAJOR Factor in the fight and if a giant Xenon Fleet enters the Sector, time is of the essence to get as many large ships to the frontline as possible.
But also.. like Defense Stations adding more defense modules over time, these Jump Stations can have more Jump Modules added over time.
If players can buy / build something, they will absolutely go ham with it. Your arbitrary numbers just can't match the sheer ridiculousness of player production once it gets up and running. Your solution to limit jump beacons wouldn't be helpful that much, as it just makes scaling up take a bit longer.
The X3 AP approach stays as the best solution possible when it comes to beacons. No buying, no building. Go and try get them with your highly expensive marines, fighting some of the most annyoying ships, just to even have the chance of getting a single beacon. And if you succeed, you get a very powerful, but also extremely fragile item. Which you'd want to protect at all cost. That is a fair trade off if you ask me.
And it's like you said, the X4 Universe is only going to get bigger each expansion that it'll be bigger than X3 eventually.
So Infrastructure to try and make it faster to reach your destination requires allot or resources and requirements to be fulfilled. Plus War can seriously set back the project if such modules get hit by Xenon attacks or by any other enemy Faction trying to slow your advance down.
Having jump drive access to gates only would be already enough to get down future travel times. By a lot. Station modules that act like beacons are not a good idea. Stations can be turned into fortresses, regardless of their type, as there is no hardcap on defence modules as far as I know. And even if there was, you'd still make beacons more common through player production. That should never be the case unless you completely design the game around them.
