If I made a multi-block that was pseudo solar powered via having solar detectors saying they see day-light as a block,
would I have to manually reform the multiblock after changing to night and back to day?

Later answer, but better late than never: Yes. You'd have to make something that changed the blocks in the machine during day & night. There is no way to detect this kind of things with MM itself and make the machine "dependent" on it being night or day or something. And such things are not going to be added by design.