If conduits transfer damage to the reactor large, centralized reactors won't be any good no matter what their power output per tile is like. Since a single reactor is a single point of failure it has to be more defended than the many reactors used in a distributed power system to compensate. If power conduit or connected storage hits can detonate the main reactor centralized power will have the worst vulnerabilities of distributed and centralized power.
I would suggest making reactors boost adjacent reactors for better scaling to large ships. Let reactors boost adjacent reactors.
- A full reactor adjacent to at least one other reactor that is not full pushes the batteries it would produce if not full to a random non-full adjacent reactor.
- Each reactor increases the maximum conduit length and power production of adjacent reactors.
These rules allow clumped 2x2 reactors to fill the purpose of larger reactors without adding a new part. The first is important to allowing large clusters to use all of the reactors. With these rules reactor design is nontrivial, but very large reactor clusters become possible.
It's probably necessary for large ships to offer conduit junctions to allow a number of conduits that can fit in a ship interior without consuming all of the space needed for things like crew quarters to serve as many storages as a distributed power design would have reactors. A conduit junction would act as both a storage and a reactor with maximum outgoing conduit length inherited from the incoming conduit. If conduits lack directionality it would have to have an incoming side and three outgoing sides.