I had recently seen an article talking about "service areas" and it got me thinking about this again; so upon searching, I find your reply mentioning the same. After messing with this function, this is really a good solution to the issue! It requires a change of thinking on how to do it - basically considering each hydrant unique with its own area of effect. when combined with all other hydrants, it results in nicely defined gaps in coverage. Exactly what my end goal is! It negates the whole 'next in line' issue - like i said - a change in thinking about how to get the end result.
And it is fast too - I've done large sections for testing that process in just a minute or two.
So if anyone is looking to analyse gaps in hydrant coverage, this so far, seems to be the best way to achieve that.