Thanks for taking the time to answer Grant, informative & interesting. I guess the choice is a swings & roundabouts thing. Less wiring/easy replacement vs having to replace an entire control box should a single 'micro relay' fail instead of a single replaceable relay. The 'modern' way.

Certainly a valid choice, & a neat solution.

I suppose if a micro relay did fail, it wouldn't be to hard to 'dump' one circuit & move wires & fuses to keep a more essential circuit in operation until a spare could be obtained. (Assuming all the micro relays are similarly rated).