Yarlen is concerned that by removing forced Phase Highways, we will only have chaos (hehe whack-a-mole). I have to personally say that the idea of unlimited options for attackers is kind of appealing because it would actually be original and realistic

But myself, DRavisher, Major Stress, JSInvader and others all offer valid ways of avoiding making game strategy 100% offense.
Jump ranges can be limited, with extremely expensive research tiers gradually reducing that limitation. The highest level research tier should offer unlimited range and the ability to reach other star systems.
Furthermore, Jump ranges outside of Phase Highways can be limited by speed.
Also, Phase Highways can still be a part of the game, just not the only part. So, if you build Phase Highways Projectors between your colonies, this will give the defender the enhanced travel speed they need to organize a proper defense when their backwater colonies are attacked.
Oh, and here are just some of the problems with multiplayer that forced Phase Highways are going to cause. Please note that this part is copied from the "Phase Highways in space is a bad game concept!" topic.
You could play Team games and never see or be able to reach your teammates. Imagine how the poor player who gets stuck between two hostile teams with no ability to expand or reach his own teammates is going to feel.
Even regular non-team multiplayer is going to suck with forced Phase Highways. One guy starts at the end of a highway, and has an opponent in the next planet over. This second guy just fortifies his homeworld a bit while expanding into other nearby empty planets/asteroids. Soon, he has enough over whelming force to turn around and crush the trapped first guy who never had a chance.
Alliances in standard multiplayer make absolutely no sense with forced Phase Highways. You have to go through your neighbor to get anywhere anyway, so why not just take him out. It is too dangerous to ally with him and leave him behind your lines. Otherwise, the guy allies with you, you go through his system to attack somebody's far off colony, and then he sends his fleet to take over your undefended colony that he is supposed to be protecting.
Gone are the usual multiplayer unspoken agreements of mutual non interference because they both HAVE to go through the other guy to get anywhere anyway.
Also, don't forget the threat of stalemates that forced Phase Highways offer us. Sure, weapon platforms aren't super powerful, but they add punch to a defensive fleet. Not to mention that the defending fleet will already be positioned properly to maximize their power. Also, defending fleets will be able to pick off the earliest attacker ships to arrive with massive focus fire since the attacker fleet never arrives at the same moment. All of this is to say that the defender will have the advantage = stalemate.
So, forced Phase Highway = bad, unoriginal and less than Epic. Something needs to be done so SoaSE can become this decades benchmark for Space Empire games.