[X][FLEET] Many Fleets. Smaller fleets will struggle to address determined resistance and force you to bring in reinforcements from other fleets, but can be produced in greater numbers, allowing you to more reliably cover ground.
[X][MARINES] Grant Tannuvael's request. Now that the fight is moving beyond your space, there is a need for an elite, navy-integrated ground force responsible for void-borne operations. Will require an eventual fleet-wide refit.
[X][DOCTRINE] Retain Territory Defense Doctrine. Ultimately, Virmire remains a world with its back against the wall, and any offensives you make must be made only once you are sure of your position. Turtle up, and turtle harder. Make your space a brick wall, against which the Rachni might break themselves. You will serve the larger struggle with the forces the Rachni must devote to bottling you up. Will not cost additional resources to implement.
[X][DOCTRINE] Adopt Raiding Doctrine. Virmire faces a situation outside the planning of conventional military thinkers, and thus it is only fitting that you adopt a doctrine designed by Virmireans. You cannot hope to face the Rachni in the open once they truly turn their focus to you. Instead focus on slipping through their lines and striking at their rear, wreaking havoc and forcing them to split their focus a thousand ways. The chaos you leave in your wake will be your contribution to the struggle.
[X][MARINES] Completely reform the marines, making them a massive, elite force capable of striking any target from space without army support. Will require immediate production of dedicated vessels and a navy-wide refit.
[X][FLEET] Large Fleets. Large fleets will be able to secure their zones of responsibility with greater ease, but given the administrative difficulties in spreading them out across multiple clusters, and the inescapable fact that you'll be able to afford fewer, you will be able to cover less ground.
[X][DOCTRINE] Adopt Ground AssaultDoctrine. Eventually, the fight must come to the Rachni's home worlds. You do not want to lose territory and see the Rachni fully re-establish their presence there within the year. You do not want to spend half your strength watching over blockaded worlds. Your resources are precious enough as it is. Virmire's armies will march to the thunder of mass accelerators, and smash the Rachni wherever they may be found. The wounds you leave will be lasting ones. Your contribution to the war will be the bleeding gashes you tear out of the true heart of the Rachni's strength. Not in and of itself more expensive, but you will need to spend a lot of cash jacking your army and marines way the hell up if you want to succeed here.
[X][DOCTRINE] Retain Territory Defense Doctrine. Ultimately, Virmire remains a world with its back against the wall, and any offensives you make must be made only once you are sure of your position. Turtle up, and turtle harder. Make your space a brick wall, against which the Rachni might break themselves. You will serve the larger struggle with the forces the Rachni must devote to bottling you up. Will not cost additional resources to implement.
[X][DOCTRINE] Adopt Fleet Battle Doctrine. Your navy will not be the navy to destroy the Rachni's fleets. However, you will be called upon to fight the Rachni, time and again, whether or not you want to do so. If you are to survive and support the allies you soon hope to contact, you will need to be capable of holding your own in a stand-up fight.