DCS2 isn't a physical system it all based on the meter listening to chat, and sensors dectecting targets.
From past SIM rules even arrows aren't physical anymore. Bows and Arrows are pretty darn annoying in DCS systems, they're litterally better meele weapons than swords are. Essentially you can account for something like a 3-5 meter radius splash damage in a complete circle, compared to an arc(usually 90 degrees to 180 degrees) the same size on a sword.
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I would probably say stamina system is probably the best proposal. Essentially you can have the stamina damage come from enemy meters when hit or from your own meter.
From your own meter this means that you can't have interferance from cheats, but it discludes the ability for bows to damage stamina. Essentially you can account for arrow/bow damage coming from further than 10-20 feet(whisper/say range), since bows are still required to to use channel 20 to damage people(usually still sensor+splash damage but that's just part of DCS silliness).
You could go for the enemy meter damaging your stamina. You're going to have the same issue you're facing now eventually, if you get any amount of popularity. You're relying on more channel usage which means you're going to take more script time building, string-to-listing, and testing strings than above.
A last ditch effort would probably be listening to mouse clicks, but not every click is a real swing or fire. Swords are easy to validate, arrows will once again require a reply from the enemy meter. End result you're better off not bothering decting mouse clicks.
With stamina you also have the whole GUI issue.
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You can also decide to just go with a global logger and damage reader, that displays a persons DPS and shortest time between swings(after having this information public+known I've seen cheaters actually dealing less damage than real players for fear of getting caught). Then have users judge who is cheating and self enfource. This is pretty much the only thing that works with DCS systems, they're so public and so old that users have soo many silly things.