[Strategia_In_Ultima]

Alternative 1. Interstellar FTL travel is possible, and it's none too slow to prevent turtle-breaker fleets from having to spend decades in interstellar space.
Result: Everyone's going to have fleets scooting around in interstellar space to avoid WP defenses.
End result: WPs reduced to civilian transport networks only, system defense becomes a b**ch, borders change faster than you can keep track of, fleets start popping up and disappearing everywhere etc.

Alternative 2. Interstellar FTL travel is possible, and it's not too fast to avoid the mess of the End Result of Alternative 1.
Result: People still use WPs.
End result: When you dispatch a turtlebreaker fleet, it'll be rather severely outdated by the time it reaches the turtler, and he'll sweep it aside even though he's outnumbered 3 to 1. To build a fleet capable of breaking a turtle, you'd have to devote your entire production over several years to this goal, and you'll end up dead as the other empires'll take advantage of this to invade.

Alternative 3. Interstellar FTL travel is impossible. System grav shields have an on/off button.
Result: SE as we know it.
End result: Turtlers gain vast amounts of power as they can now strike out from a turtled system without fear of retribution.

Alternative 4. Interstellar FTL travel is impossible. System grav shields have no on/off button.
Result: SE as we know it.
End result: People will still resort to turtling.

Alternative 5. Interstellar FTL travel is impossible. System grav shields use up vast quantities of resources each turn.
Result: SE as we know it.
End result: Turtlers will not be able to sustain a turtle if they don't have a nice resource base spread out across several systems. Turtles will become a lot harder, but not impossible.

Alternative 6. Interstellar FTL travel is impossible. System grav shields only last for a set amount of turns after which they fizzle. The structure can be scrapped.
Result: SE as we know it.
End result: Turtlers will have to deal with a vulnerable period every so often, unless they synchronize queues on multiple planets.

Alternative 7. Interstellar FTL travel is impossible. System grav shields only last for a set amount of turns after which they fizzle. The structure cannot be scrapped.
Result: Non-turtlers using a system grav to prevent a solar nuke from going off will have to deal with the fact that the slot they use to build the grav is lost.
End result: Turtlers will have to deal with the fact that eventually, they'll run out of space in their system, at which point the entire system becomes utterly useless, unless he's got a few planet-killers, planet-creators and colonizers tucked away somewhere. Nuke all planets, create new ones and rebuild your empire. Vulnerable period lasts longer and turtlers are more vulnerable, however as stated above non-turtlers will be more vulnerable to solar nukes and planet-killers.

Take your pick.