I just thought of something...
Since missiles have just a very little bit of power even without engines, would it be possible to make a suicide ship carrying a size 100 warhead to run up to the enemy ship and blow it to smithereens?
You need speed and maneuverability to hit the target, even if launched at point blank. All you could save on is fuel.
And one big missile isn't ideal due to point defense. It only takes 1 AMM to shoot down your super missile. Or a single hit by final defensive fire from a laser or gauss weapon.
A more effective way of doing things is to have fighters armed with short ranged missiles on box launchers, with a very long range active sensor on the carrier. The carrier spots the targets and the fighters fly in close and fire the missiles. The carrier can stay out of missile range of the enemy, and the enemy can't shoot down the fighters until they're close unless it has specialized sensors and fire control. Since fighters are size 10 or below, they can often get really close before being detected. Even facing high tech ships fighters can get a lot closer than large ships. Against a ship with sensors tuned for larger ships you should be able to close safely to 10m km or closer without them shooting you, against ships tuned for FACs or missiles you can usually safely close to 40m or 50m km. It all depends on the size of your fighter and what their sensor resolution is. The only problem you might face is if a race has ships deployed specifically set for dealing with fighters, in that case they might have big sensors set up to detect your fighters out to 100m km or more. I haven't seen too many of them though.
I usually like having my fighter missiles set for around 40m km. They can fly in to that range, fire their ordnance, and turn around to return to the carrier. Even if enemies detected them at 40m km and started firing, chances are your missiles will all hit before theirs reach the fighters since they will have to chase them moving away while the enemy is probably moving toward your carrier still.
I remember playing one game where an NPR deployed some fighter killing ships that were detecting and firing at my fighters at 110m km, but the missiles they were firing only had like a 30% hit rate with warhead 6 and my fighters were armored enough to take several before going down - so I still didn't suffer too many losses. I remember one time having two of their ships fire around 240 missiles, about 6 each, at my 40 fighters - and they all just completely shrugged them off and kept going, to be repaired when they landed for reloading. My fighters were really cheap to produce too, I had hundreds of them waiting at my planets docked in PDCs maxing out their training just waiting to replace losses aboard the carriers (or be deployed in defense of the system). I had their engines with a 100% explosion rate, so all it took was one engine hit and they were goners - but I still didn't lose many.
On the topic of survey ships, I like making teams of small ships early on. One ship has a jump drive and extra fuel storage (so it can act as a tanker) and is commercial, another has geo sensors and is commercial, and the third has grav sensors and is the only military ship. The actual survey ships have nothing but engine sensors and fuel, so they're faster than you could get making one with an early bulky jump drive. I'll group several geo survey ships with one jump ship, then several grav survey ships with another. You can give the order to detach non-survey ships to have them ditch the jump ship at the gate, then "transit and divide fleet" to have them split up. This keeps the orders, so they'll split up and go about surveying the system separately. When they run out of stuff to survey I just order them back to refuel from and join with the jump ship and then they're off to the next system. When the fuel starts to run low the jump ship can head back, refuel, and often get back while the other ships are still busy surveying. The grav survey ships have to return every so often for overhaul, but since they're faster I can just have the jump capable ship ferry them to the nearest jump gate and have new grav ships meet it there. They swap out and the jump ship heads back out while the old grav ships go to get overhauled.
I also like making a military sensor ship to tag along with the grav survey ships, with a big thermal sensor and basic missile defense, to sweep the system for potential enemies before I send in the geo survey group. If I don't I'll occasionally lose the geo surveyors to mines and precursors and swarm and stuff. I only put basic defenses on it designed to deal with stray mines, not enough to fend off a real threat.
The only downside to doing it this way is you need 4 separate shipyards, but they don't need to be very big.