So I think we should build a pair of monitors based off the Spatha hull:
-[] Buckler Class Monitor (42 M)
--[] Spatha-class Hull (5M)
--[] Standard Macrocannon Battery MkII (5M)
--[] Standard Macrocannon Battery MkII (5M)
--[] Scaffold Armor (2M)
--[] Bubble-type Rapid Shield (6M)
--[] Corona-Pattern PD Array (2M, Replaces Warp drive)
--[] Repair Deck (2M)
--[] Militarized Engine (3M)
--[] Groupsight Combat Bridge (4M)
--[] T-100 Auspex (2M)
--[] Redoubt Life Support (3M)
--[] Bastion Housing (3M)
2 of these would be only 84 M and probably be more dangerous than 6 refitted monitors due to better speed and concentrated firepower. Note that I downgraded the sensors to save cost since they don't need long-range sensors due to having short-ranged weapons. They mount Corona PD because we don't typically have much fighter support in our defenses.
Also, using these would let us protect our shipyard and the planet, unlike a stationary platform.
On the topic of research, it occurred to me that we should not bother continuing to research thermo-cavitation shell manufacturing, for the following reasons:
1. Building the shells without Mechanicus involvement will need 5M. That is too expensive to be justifiable. I mean, the new torpedoes cost only 3 M each, yet we barely built any new torpedoes despite their relatively low cost.
2. The whole point was we were hoping to use the shells more often, but the 5M cost makes that impracticable.
As such, we should instead research explosive shells, since they should provide a damage boost without being too expensive for a mass rollout.
Still, next turn we will need to dedicate as much as possible to shipbuilding. Even if there are requests to provide M in exchange for research slots, we should not take them, because right now we need M more than we need research slots