Thank you! You bring up some very good points to which I can only say, no strategy or formation is absolute. When laying out designs and plans, a good commander must know, that there will be deficiencies their plan/strategies. Their main job will be to minimize those deficiencies as much as possible to minimize damage to property and those serving under them. Now, to address your points one by one.
1 & 2) I'll answer both of these points as my response will play into both. You make a good point about the Polaris having mostly forward facing weaponry, but lets treat this like a game of chess. The Polaris is the Command and Control ship in this scenerio, your King. No successful chess game has ever been won by leading with the King. (If so, I'd be dying to play that game lol!) You are correct, however, about capital size radar/sensor package. I would argue that moving the Polaris from rear guard to the front just to gain an extra two or three hundred meters of visibility isn't worth potentially risking your Command and Control ship to the possibility of heavy incoming fire. The forward Hammerhead is a pawn in this formation. Pawns are typically used to build a defensive stance and have the potential to become a very effective offensive piece if phalanxed appropriately. They only real advantage the Polaris has over the Hammerhead are its torpedoes. Take that away and the Hammerhead would shred the Polaris in a toe to toe bout as the Polaris doesn't have any where near the same firing arcs that the Hammerhead has.
A secondary reason for keeping the Polaris rear guard is the element of surprise. If the enemy approaches from the front, immediately all they will see are Hammerheads and some fighters.Even if they scanned ahead before moving to intercept, they weigh their options on whether to continue the attack or not, they may be hasty and rush in. Once the Polaris reveals itself from behind the resource and begins to loose its torpedo salvos, that could prove to be a psychological victory as well as a complete one, but that's a trick you can only play once. If you've laid all your cards on the table too soon, the gig is up. Keep in mind, all Hammerheads will remain in formation. So a 360 degree defensive perimeter around the resource would be constantly maintained. In the image, I have posted a flight of four fighters to maintain rear guard with the Polaris. Their objective will be to stay with the Polaris in the event it needs to break away in defense of the rear. If that were the case, that 360 would still be maintained. In my original post, "Aegis Hammerhead weapons loadout", I outlined the weapons of choice, and for the five Hammerheads on the perimeter, the M6A Laser Cannon would prove to be a great choice due to its rate of fire and range.
3) Placing Hammerheads above and below is another viable option. But keep in mind that this formation will be moving forward, so I'm not completely understanding the concept of "Also have the top of the Hammerhead facing away from the Orion. To give the Hammerhead top turret a better field of view." Imagine a diamond shape and at the center of the diamond is a ship you want to protect. Then imagine the a Hammerhead to the left and right. With the firing arc they possess, you would still have the ability to fire above and below the resource. This is simply the formation I've chosen to illustrate based on the tools I had available to me at the time. In short, yes, placing a ship above, below and on either side could also prove to be very effective. It just depends on the situation. With the advancements made in the game with the volume-metric cloud i.e. The Coil from the vertical slice, it would be purely situational to choose to stack ships in an environment like that.
4) I would submit opting for balance. Two Harbingers and two Wardens. In any military formation, the scouts have one job. Scout. Observe and report. They are the eyes and ears of the fleet. If a fleet can not see, they can not prepare. If they can not prepare, they can not fight. If they can not fight, they have lost their mandate. If met with enemy resistance, the scout force will either fall back to the main fleet if heavy resistance is met or they will evade, seeking an alternative route to maneuver around the enemy contact. They also check to see if alternate routes are safe to travel through. While they could be used to assist in defense of the main fleet, that should be an absolute last resort. Just because the main fleet has so much fire power, doesn't mean it MUST be used, except as an absolute last resort when all other means have been exhausted. Could you imagine if Britain and France (for example) went to war? And at the outset of the first engagement, the U.K. launched nukes? A little extreme, no? But I digress.
Suppose we go with your method of thinking on this part in particular. The main fleet is attacked and is surrounded. The Polaris' sensors are offline and they are flying blind. Calling the scouts back to fight may not benefit you as much as you might think. However, finding an escape route to rendezvous with allied back up could prove more beneficial. Casualties may be extreme and ships may be lost, but if we can hold the line long enough for the resource to escape, that'll be worth the loss. Only and only when there is no other option would I pull my scouts back to the main force. There isn't a military operation that doesn't heavily depend on what scouts and field commanders see and believe to be the best viable option.
5) The Banu Defender would be a good option, but as you've highlighted, we don't know much about this ship yet. Since the Aegis Vulcan was released, we could infer that it too would be a good ship to bring along for the ride. I would place my faith in the logistics units within Imperium. Making scheduled stops in hi-sec to refuel or schedule refueling in dangerous parts of space. That scenario would depend on the flight pattern. Where are we flying from and where are we flying to. That part would fall under a logistics post. Another very important part to mission planning that I have yet to complete a writeup of for. Stay tuned for that one, lol.
6) This point would really depend on how much the client is willing to spend. The running cost of a Polaris would be much higher than a Retaliator. The Tally has 7 crew as opposed to the Polaris' 14. So you'd be more than tripling your cost on crew alone. Not to mention the fuel, ammo and (potential) repair costs. All of this must be factored in as well. If the client is willing to pay for all the bells and whistles, then I am happy to give them the most bang for their buck, so to speak. But it would have to make sense and be tactically sound. Otherwise, I'd just throw an Idris, two Polaris, four Hammerheads and a bunch of fighters at every situation and hope for the best.
I hope this was helpful. I very much enjoy this type of theory crafting. I must emphasize that there is no automatic 'I win' button to these types of posts. All one can do is try to dissuade any sort of violence by a show of force. In this game, we all know there will be those who try to make a name for themselves. We'll just have to keep a clear mind on the mission and the objectives we plan to meet along the way and let our strategy guide us.