As a solution to that problem, why not simply greatly increase ship mobility?
It is my understanding that ships have been made so slow to prevent doomstacking, but it turns out it didn't solve the problem at all anyway, in fact slow reinforcement arrival speed makes it even more worthwhile to doomstack and adopt the Schlieffen strategy and smash your opponents one by one as fast as possible like OP described.
So just make space smaller. I'd rather see fleets move at a pace similar to armies in EU4, where it doesn't take me 3 years to reach an enemy.
The Sci Fi nerd inside me is refusing to make the system more unrealistically small. But yeah, that's why I'm proposing one way or limited gateway (or wormhole). That at least alleviate of "taking three years to reach the enemy territory"
Note that in my game, by the time I can build gateway, I basically revert back to a doomstack tactic. Build one in my home system or the L cluster terminal as the home base for all my fleet and the spam built gateway in a frontier system and then all the important system. That with jump engine make my doomstack very mobile and rendered the mobility a non issue. But if I reach that point, I almost considered the game won already.
That said, if mobility is a problem, the possible solutions are:
- The limited gateway or artificial wormhole
- Make ship faster or the system smaller (
- The highway idea, Make the hyperlane registrator (that starbase building that reduce FTL cooldown) more effective, maybe even chaining them to a single hyperlane corridor that ship can travel without going across each system.
Any other idea?