the space combat is the main content for the war in endless space2,but the space combat must happened  when two fleets in the same solar system.some people may say we have behemoth ship could launch the Beyond visual range attack 。but thoes attack could destory the plants and spend too much resource and it is overkilled.so l suggest the developer teams add the long rang cannon ship to each majory faction which is have limited  long rang attack ability and  the size of thoes ship should as large as carrier but its major function is launch the long rang beam or cannon boll to another star system to damage the emeny fleet witch is detected by you pobs or radar .thie new long range assault ship also have its draw back which is low  moveing speed .only can have few weapon to defened himself it only have very limited self defends ablity .but it can play a role as a long range sinper to shoot emey fleets from another  solar system.  

    if the space combat add beyond visual range attack .the game will be much more better than before.

The primary dilemma you're going to face with this suggestion is the way movement works in ES2. The weapon you're proposing would be insanely powerful if it abused starlanes and free moevement paths to hit fleets that couldn't reach it for several turns. You would also need to consider the logistics of such an attack, the sheer distance such an attack would have to cover would be preposterous. This is handled somewhat with the Obliterator because it takes several turns for it to reach its destination (usually) and it targets immovable objects (like planets) whose orbital trajectory can be calculated. 

Something like a fleet would be moving way too fast and unpredictable for an attack at that range to land with any level of regular predictability. 

In terms of the gameplay, I think this would diminish the gameplay more than enhance it. It would turn the game into a series of snipes and star lane control rather than actual fleet composition and skirmishes. 

the new long sniper ship should also take few turn to lanuch the fire .and the fire only make damage to the fleet whitch is bord the system,when the fleet is moving it will miss the shut,and the fire is take 2-3turn to reach the targeted area  and the shot range of the new ship is very limited .when it is fired the sniper ship also will stop moving for few turns.it is not so powerful as you thought.

my second thought is the major function of thoes kind of ship is providing the long range fire support when a fleet combat is happening .the sniper ship could shot the emeny ship from distance just like citidal do .