Raiding , is a fleet objective to damage an enemies economy through the destruction of resource structures whilst avoiding confrontation with enemy fleets, using a small fast specialised group often engaging with the help of distraction and opportunistic timing.,

A successful raid will damage the economy more then the losses of the ships. A unsuccessful raid will damage their economy but the cost of your lost raiders hurts more.

How is raiding now?...(non-exisitent)

Ever played the AI to find when they send 2 cobalts on a raiding mission , the cobalts spend 10 minutes trying to take down 1 extractor , which gives you ample time to pick a convenient time to use your steamroll fleet to just pick em off.
Have you ever tried to send maybe a small fleet round the back , only to find theres nothing it can kill. Have you ever thought maybe the fleet points you spent on the small raiding party would have been better off as part of your steamroller because all they managed to do was kill one 250 credit asteroid and a builder. Does it feel like when a ship pops out of the shipyard its only mission is to be part of a steamroller fleet. Does it feel like two steamrollers are at a stand-off just waiting to try and double each other in fleet points , or waiting for an allied steamroller before 2v1ing steamrolling...and theres nothing else you can do with your ships other then this.

So how can raiding be implemented?

It is quite simple. ( not all need to be implemented but just ideas subject to balance)
resource asteroids health: 2500 hp -> 300 hp.
resource building lagtime: ,after a mine is destroyed , takes 1 minute before the mine is rebuildable on. (happens in EaW).
resource asteroid increase cost of replacement: As asteroids are replaced their cost increases. 250->300->500->1000->2000 capped.
builder replacement cost: maybe 1000 credits to replace a builder. (builders can also be another raiding target).
Trade posts reduced in hp
Refineries reduced in hp

By doing this , resource asteroids become vulnerable to small attacks. Players will have to be wary of keeping thier fleet bunched because it exposes the two other entry points into their empire to small attacks that do big damage.

To summarise , raiding is a HUGH element in RTS games because it breaks up the monotony of stand-offsm gives players something to do with ships other then macho up their steamroller , gives players the chance to get-back against a high eco player , is a tactic that is non-dependant on your maximum fleet cap ,introduces the ideas of chasing ,dodging , distraction , the theory of speed over power ,a counter to steamrolling , something that requires you to scout alot more and be warym and lastly a skill that will continually improve with players as they play the game more.

Sins needs it. I know theres like no dev time left , but this really needs to go in because gameplay at the multiplayer level is very monotonous and stale. Its almost like having Supreme commander with invulnerable resource buildings atm.