There are already 'interdictor cruisers' of a sort available. The Guardian with it's Repulsion ability, the Enforcer with it's Inertial Field, the Subverter with Distortion Field, and the Robotics Cruiser with Demolition Bots can all prevent enemy phase jumps.

Dosnt the TEC Carrier have that ability? Embargo?

As it is, I find it's way too easy to play cat & mouse in this game. The AI constantly runs from you and it gets old quick. A way to slow their escape or prevent it for X number of seconds would be a blessing. Anti-matter ability on a new ship? Prevents all phase jumps for 10 seconds. 45 second cool down. Costs 30-40 supply. This way having one is truly tactical. Do you have a slightly weaker force with the ability to make your enemy unable to flee or a slightly stronger fleet? And if you could afford to have two of them in your armada.. nothing would escape but if you met a fleet without an interdictor you may lose.

Why on earth do you want a phase jump inhibitor ship? That makes no sense - there is already a phase jump inhibitor. You would not be adding anything to the game by creating a ship to do what a phase jump inhibitor already does. You might say "well the current phase jump inhibitor is useless," and I agree. But adding a new ship isn't the solution - fixing the phase jump inhibitor is.

If the current phase jump inhibitor is useless, why do you think the devs would consider giving you a mobile one that is actually effective?

There is already a mobile Phase Jump Inhibitor. The Serevun Overseer with it's Jump Degradation ability technically inhibits phase jumps(slowing the enemy's speed in phase space by 50%), but doesn't stop them.

The same effect can be obtained, however, by using Jump Degradation when the enemy is retreating and chasing after them at the same time. Since they'll be traveling through phase space at 50% of their normal speed and you'll be traveling at your maximum speed, your ships will overtake them and when the enemy reaches their destination, your fleet will be waiting there from before. That exemplifies the Vasari being the masters of cat-&-mouse, with the 'cat' being everywhere at once.

A mobile phase inhibited, similiar to an interdictor cruiser would be great. I could see many uses for said device. For example one could fly aways outside a gravity well, and pull invaders back into space well before a planet. This would be an excellent way to ambush opposing forces or slow them down from reaching your colony.

It is indeed a good idea. However i find i dont play too much cat and mouse as i am more defensive. I like Ion bolt, cripple an enemy cap ship and take it out.
I find myself at the moment splitting my fleet in to two smaller fleet. Have one assualt the enemy fleet and the other wait for them to hype out once you have caused enough damage to them. Mind you, this only works vs AI and only in defence of your own planets.
For attacking-If they run...and i still get the planet. No problem. If they come back, it will be defended and at some point my fleets box them in on thier remaining planet(s) and crush them.

I think that may be too extreme. Keeping it contained to one unit means that the enemy can target it, if the battle is going poorly, and attempt to run. Having it be an ability on a cap ship means that no one would really be able to escape. I'm ok with people running, but I think the game would really benefit from a passive AOE anti-phase jump unit.

Sorry, SentrySteve, but I think you misunderstand me. The ideal was not make it impossible to jump, but increase the time need to make a jump if the capital ship was in the system. I was just trying to add more depth to an already deep game. The mouse(fleet trying to jump) would have to choose between target one ship during the fight or fighting it before jumping(ie more time till jump) or waiting while the time need to jump is reached. The cat (fleet trying to destroy the other fleet) would also have to make a choose, to bring all there capital ships together, in order to increase the time need to jump, or spead them out more to get more enemy fleets. Because right now as it stands, there is no reason to spend out your captial ships. Meaning that it there are player going around with 16 capital ships of doom, with no reason it any other way. In this way you would have to chose between 16 doom fleet, with only being able to get one mouse, or sprend them out to get more, with the higher risk of those ships becoming mouse themselves.

But you are right on the let not make it impossible to jump. We need to find the middle ground form way to fast to jump( where we are right now) and impossible to jump. So here are some rules, in my mind to fix the problem.

1. Have the jump inhibitor only increase the time to jump, not make it impossaible. What I added before was to give the player the chose in how to reach that goal.

2. Link the jump inhibitor to something in the fleet. We would like longer fleet battles, not longer for our fleets to get to the battle.

3. Make it so that both the cat and the mouse will have to make some new plans based off this new system.

Welp, I think that the new patch is kill the cat'n'mouse game, so we may not need one. It would be kinda cool though.