To me these are perfect.

The Core Resolution Mechanic is just 3 sentences written in such a clear, applicable and unforgettable manner that the whole thing feels like a common sense.  D20+modifier, casualties dice, tie casualties. Useful extra notes on modifying Modifiers (sic), Casualties Dice, making it an interesting backdrop for Player Characters to let them shine and make a difference or to feel small, speeding and dilating times.

This is not a supplement that's needed to be referenced at the table, this a little collection of rules and ideas that makes your table ready for things that could have been too slow, too abstract or too heavy on GM-fiat before.

+

I've heard that Errant, Knave2e and Runehammer also have rules with various levels of abstraction for bigger battles, skirmishes and things related (up to the rules-lite Wargame approach in the case of the Runehammer) but can't comment on them just yet.