At this point in time humanity has four or five Dreadnoughts operational. So LLPs are roughly a one to one match vs. Alliance Dreadnoughts. Still to be a bit more conservative lets say it is a two to one match.
Assuming that holds true then roughly speaking eight Lite Laser Pyndas should be a match for one Reaper Dreadnought. Thus to mach a force of 20,000 of them we would require 160,000 LLPs. In terms of Production capacity that is 652.6 quarters worth of Space Factory III production.
So if we could keep a dozen Space Factory IIIs operational during the war it would take ~14 years to produce enough LLPs to match the low end figure for Reapers. That isn't great but it also isn't a century of conflict.
If we want to wage a conventional war then our goal should be to improve our weapons technology. The fewer ships we need per Reaper Dreadnought the more reasonable a conventional conflict is.
While this is true, I'd be
incredibly disappointed if the Reapers had as little defense against even our most basic laser weapons as human / Citadel races do.
I've sort of been hoping that we'd be required, or at least encouraged, to develop all of our weapons technology categories, at least a little, rather than simply being able to throw more power at the problem:
- Main-gun grade laser weapons (higher frequencies and powers) - Useless against TIR shields and protected against by thermal superconductor tech, but excellent for burning an enemy down after their shields are broken
- Repulsor-based particle beam weapons - Great for breaking down shields, but less awesome against armor
- MAC weapon mods - Slower than lasers and particle beams but with more "stopping power", essentially switches places with GARDIAN defense systems to be the equalizer in closer-range engagements. Also good for bombarding planets and other stationary targets.
- Artificial biotic giant mechs - Specialty weapon system to add flexibility in certain situations. Biotic Charge allows short-ranged, precise FTL hops for tactical-scale maneuvering.
- Unibeam weapons - Hero-only weapon that requires an on-site theoretical physicist (eg. Revy, Conrad, Gaver Dor, Mordin, etc) to keep the system from doing Unknown Strangeness to everyone.
Lasers are
currently a miracle weapon against all Citadel and Terminus races, but frankly the Reapers should have already fought against laser-wielding civilizations in the past. After all, both the Salarians and the Geth were on the verge of setting off the same "laser scramble" that PI is setting off right now, although they would have probably been forced to start with Laser Cruisers rather than Laser Frigates due to power generation issues that we can solve with the Arc Reactor.
But against the Reapers? They'll have thermal superconductor shielding around their shield emitters to protect against lasers, making our current laser frigates' dreadnought-killer tactic ineffective against them. They ought to also have TIR-based shielding to employ if the harvested species had lasers, because they couldn't have possibly managed to perpetuate the Cycle for a million years if they didn't.
All of this is of course up to
@tri2, but it seems like a shame if we were able to solve all our problems by just throwing a bunch of research points into more laser dakka and not even looking at the rest of our tech tree.