@sdetweil Thank you Sam, I was getting the impression that each module could only handle one unit type, but appreciated the confirmation.
By way of an update, I did explore your suggestion of a second instance, there are a few posts describing how to duplicate the default modules. I did pause this aspect of the project to work on other aspects until I worked out how to implement it (the thought of near exact duplicate modules at once was ghastly, and the idea of stripping the second to just imperial and merging it somehow with metric was headache inducing).
I came back to this after finding MMM-Pages and it cycled quite nicely every 15 seconds between the metric and imperial display. Happy partner, happy me.
Well, that was until I installed the MMM-GoogleTasks module which broke MMM-Pages. But, your input on the MMM-GoogleTasks not compatible with MMM-pages, MMM-Carousel, or MMM-ModuleScheduler thread solved that!
Anyway, thank you. Much appreciated on both counts.