I didn't suggest designing special long ranged missiles but rather simply adding an internal nuclear warhead to those "robotic monsters" to take out targets. No need to wait and use ramming only as a last resort, against valuable enough targets it would be the primary attack mode - with an engagement envelope that would be unmatched by any ship mounted weapon. Though nukes are rather expensive so not all drones should be equipped like that.
I wouldn't even go that far. Simply equip the fighter drone with wing mounted Tac Nukes. The ships will then still have the flexibility of a fighter, while also retaining the ability to ram or be deployed in a conventional role.
But the truth is, I'm loathe to equip anything with a nuclear device. Until Bolan explodes and the Succession War becomes a game of tit for tat, there's the possibility of keeping the nuclear genie in his bottle (at least when it concerns the Republic.) If the Republic maintained conventional attacks, albeit with an SDS...which include ramming....then perhaps in the short term (and that may be all that's needed) the nation can avoid nuclear reprisals. You start equipping your CapMissiles and Drones with nukes and all bets are off.
Making matters even worse for an invader you could build SC drones with long range heat expansion drives. They would charge any inbound force at extreme velocity and dump a few tons of scrap along their vector - don't even need nukes if they have a high enough speed.
That's where large drone models, like assault DropShips come into play. The problem with building hoards of them could be yard space. I mean the Republic does have a fairly large and powerful conventional navy. In the short term hoards of drone fighters could provide a very real and very potent "meat shield" with the nasty ability to hit back. This would allow the Republic to make the best of their human navy, while maintaining their yards for continued construction and repair. However, once the Republic either A.) earns a little breathing space, or B.) brings all a good portion of their yards to 100% - building DropShip-sized drones would be the next logical step.
I think these simpler drones should be well within the TR's capability to build, apart from the absolute cutting edge there will not be that much that is lostech just yet.
Well, the Republic would still have to research and develop the control systems just like the Word of Blake, and they may actually have a tougher time doing it after the Civil War. The Word of Blake benefited from over 200+ years of technical organization and refinement. When the Blakists decided to research the project they had neatly prepared technical archives painstakingly collected and preserved on the topic for centuries. The Order didn't just preserve knowledge, they organized it.
In the post-Coup Republic, information databases, libraries, military projects, etc., are in a state of disarray. Scientists and other research assets are spread to the wind. They're either fleeing for their lives, left with Kerensky, dead or just don't exist. Amaris collected an enormous amount of technical material on Terra, which Kerensky then added to before fleeing. I'm sure that pile of research formed the basis of ComStar's technical library in canon and will probably form the foundation of the Republic's, but it's still a mess that needs to be sorted, sifted and maybe even reconstructed (in some cases.)
With dedicated scientists and an organized research database, the Word of Blake was able to develop their SDS II system in roughly a decade (3058-3068/69.) I figure the Republic could do the same in about 12-15 years given the fallout of the Civil War and Kerensky's withdrawal.
However, the Republic has a huge advantage in manufacturing over the Word. Even if we played it conservatively and said that the Republic has a
functional manufacturing base of roughly 1/3 that of the Terran Hegemony before the Coup, it's still what? Roughly 3,000% times larger (100 worlds @ 1/3 = 33 - not taking into account how Terra skews the equation) than the Word of Blake's manufacturing base. In ten years the Word of Blake was able to build a fairly large SDS for Terra and a number of smaller systems on a half-dozen or so of their "Maginot Line" worlds. That's not bad for a single factory planet, even if it is Terra.
Whereas, give the Republic ten years to produce and it'll have hoards of Wasps and Voidseekers blanketing their key planets. And that's all you really need to do. Ensure your key manufacturing and breadbasket worlds are secure and it's only a matter of time before you can spread the same system of protection to everything else. With the production source secure you've got nothing but time...