Fix'd
It would help if knew what you were talking about.
First, ADS would not matter anyway, that is why Spartans have the aiming reticle installed in their Heads Up Displays.
Secondly, There is every possibility that some Forerunners survived the activation of the Halo Arrays inside of the shield worlds which is what they were designed for. Also, yes- their weapons could be fantastically powerful, yet I doubt we would see any apart from sentinel beams- If any...
Thirdly, No- the races of the Covenant are not extinct though the San 'Shyuum could possible be after their planet was destroyed by natural stellar collapse and they've no where to go (To our knowledge). Also, the Sangheili had stated they had simply vanished... The Brutes would be killing each other because of their barbarian instincts and the others would be running from the Sangheili...
'Spirit Of Dawn'!?- The Spirit Of Fire has been missing since Halo Wars -21 years from Halo 3- While the Forward Unto Dawn's aft section never made it to Earth... I would of though that was obvious...
Also, the Forward Unto Dawn was a Flagship Frigate- That doesn't mean it is going to have replacement pieces of MJOLNIR MKVI for the Chief...
And finally, There is every possibility that The Flood could be on that planetoid. The Flood is a parasitic infection which came from outside our Galaxy- the ORION arm (The Milky Way). They would have taken every possible opportunity to study The Flood for a viable defence- which, because of unsuccessful research, led them to the Halo Array and the obvious- If it can't live with out food, Starve them. With the new game being a threat to the Universe now though, it could be the planetoid is both a Sword and Shield and part of a larger system. If the Forerunners discovered that The Flood had spread to many galaxies, they would fire the large installations and wipe them out and save as much as they can - Similar to the Halo Plan. Yet we can merely speculate - but a standing rule of speculation is Don't rule anything out- Anything could happen...
TCO
Epic post.