Thank you for sharing your thoughts. Let me clarify a few points and interact with some of your ideas.
You should consider the cost of life support and propulsion to move heavy soldiers through space, then compare that to the cost of the current drone market. "Robots" don't have to look or move like people to do their jobs.
I didn't say "androids", but rather "robot soldiers". They most certainly do not need to be androids to any extent, but they do need to be capable of neutralizing defenses, adapting to changing situations, and holding territory against counteroffensives. This would require highly advanced AI, the ability to carry a substantial weapon and adequate ammunition, the ability to locomote on the ground, and battery life measured at least in days, if not months. No matter what appearance this takes, it will be expensive, and likely at least the size of R2D2. So, if one wants to compare a drone to it, it would be more like a Predator drone, which costs around $4 million, with a much more long lasting power source and extremely advanced AI. That is why I gave the price estimate I did. In contrast, a volunteer or conscript is (presumably) raised by a family or some kind of civilian system, which means the military is not paying for the cost of raising the soldier. So, in initial costs, the soldier is clearly preferable to the robot. And, regarding ongoing costs, it really all depends on cost of supplies vs. cost of energy and maintenance. That said, I strongly doubt that the ongoing expenses for human supporting supplies would overwhelm the initial cost of the robot, much less maintenance costs and energy costs. If one is talking about state farmed clones, the advantage is reduced, but even with the state raising them from birth, I still am not sure the initial cost could be overcome.
All that said, if a faction were morally opposed to loss of human life, then such robots are where they would turn to. But, barring that, I just don't see the numbers adding up in favor of robots replacing humans. Augmenting a fighting force, quite possibly, but not replacing them entirely.
Suppressive fire is a controversial and somewhat old fashioned concept. Several elite forces no longer practice it. The relative cost and damage of lasers vs bullets really is going to come down to advances in laser output and batteries. At some point, a weapon system will be able to store more destructive potential in batteries than gun powder and lead.
Perhaps for elite forces, but for the most part, if an elite force is engaging in a firefight where suppressive fire is needed, something is wrong from the outset. Regardless, we aren't talking about elite forces; we are talking about regular foot soldiers, and at least according to my sources (4 tours between Iraq and Afghanistan, two in the 82nd, two in the 101st as an infantryman) suppressing fire is still standard doctrine. The idea is to have enough lead going downrange from one fireteam that the enemy keeps their heads down while another fireteam moves to a position where they can force them back further or pick them off. The problem with a laser for suppressing fire is that one cannot see or hear the shots going by, unless a colored laser is used in bursts sustained for sizable fractions of a second, and that will give away the position of the shooter.
And, regarding destructive power, I don't doubt that you are right. The problem is that the extra power is irrelevant after it gets to the point where you punch a hole through someone. The relevant part is how they do their damage. A bullet does damage by imparting kenetic energy to soft tissues which tear and burst, while a laser bores a hole and leaves some burns around the hole. This latter wound is far less dangerous than the bullet wound, unless one gets to laser calibers matching dessert plates, which would likely be unwieldy by a soldier.
All that said, in some settings, the advantages of the laser would outweigh the disadvantages, especially where accuracy and ease of use is preferable to damage per shot. So, marginally trained conscripts and marksmen would benefit most. Even still, I would expect that a fireteam would contain both laser and projectile weapons, to maximize the advantages of the fireteam.
Long ranges are actually a disadvantage to lasers, because you can't make a self guiding laser, but you can make a self guiding slug. And bullets don't have to contend with air drag or gravity in space, so they have an enormous effective range that a laser lacks due to the inability to hold the beam steady on a moving object a light second or more away.
Good points, but the advantage of the laser is that it arrives at the same time as the warning to the enemy ship. Suppose the two ships in question were 10 light seconds away, and a rail cannon could fire at 1/4 light speed (which would be a massive engineering feat in and of itself). Ship 1 fires the slug, and 10 seconds later, Ship 2 detects the shot. It now has 30 seconds to engage its maneuvering thrusters to move out of the way, and/or ready a laser PDW turret to destroy the slug, or at minimum melt it so it cannot self-guide, and/or hit it with its own railgun shot, and/or whatever other defensive measures are taken by Ship 2. Regardless of the specific defenses, there are 30 seconds to react. For a laser, Ship 1 fires, and Ship 2 is hit at the same time as it knows Ship 1 is firing. There is no reaction time available. That is why I say, at long ranges, lasers have the advantage. At ranges less than a light second, perhaps up to one or two light seconds, the advantages of the laser are negated (6 seconds is probably adequate time to prepare defenses, and 3 seconds might be), and the destructive potential of the slug is probably preferable.
I think that one of the advances in a modern military will be doing away with bases, because you have other supply and communication options with an orbiting spaceship. Individual assault units can be much more independent when they can receive orders and supplies directly without an in-field middle man. And that's assuming they would need any supplies or instructions.
With all due respect, I think you may misunderstand the purpose of a forward base in a planetary invasion. Anything that falls from the sky has a good likelihood of being intercepted by air defenses. The initial units deployed will likely take heavy losses, even if you EMPed the area first. The FOB, then, is less about supplies and logistics as it is about not having your troops shot out of the sky en masse. The first units take the losses for the sake of taking down a part of the air defense grid, probably coupled with orbital strikes on emplacements as they reveal themselves, to give a window for a force adequate to take the planet to land before non-stationary defenses (aircraft, armor, etc.) can be brought in. But, any time a force drops into hostile territory, heavy losses should be expected.
Unless you mean people will not be interested in planets, in which case, the discussion of planetary invasion changes to colony invasion, but the premise is the same.
Monitoring the population with cheap, ubiquitous and hidden surveillance is both much cheaper and more effective than having 1 billion cloned soldiers standing on street corners.
Of course it would be. But what it cannot do is respond to uprisings in real time. Soldiers are needed for that, and uprisings will be common at first.
I don't think lab diamond chips are expensive at all, but is there some reason you'd want to use crushed stone chips for a mirror when other substances are much lighter and easier to replace? How are solar panels going to function encrusted with reflectors?
Coating a space fleet in them, however, would add up, and the vessels will likely be expensive enough as is. I don't think I was clear enough, though, about what I was suggesting. There are vastly cheeper ways to reflect a laser, but they will get burned in the process, and another hit in the same spot will likely burn through. My proposal here is not to deflect it, but to diffuse and absorb it. It must be something that can withstand extensive heat, and be clear and able to diffuse light. Hence, diamonds.
I am out of time at the moment, so I will address the other points in a bit.
