in the rule book it says

The mono upgrade may be applied to any Low-

For blunt weapons, I usually rule that a 'mono' upgrade equates to a depleted uranium core or other enhancement that increases impact.

For blunt weapons, I always reason that there's some kind of kinetic charger, increasing the effective weight of the weapon on a swing, but doesn't actually increase it in any other regard. So it hits like it weights 50kg, but still handles at the good ol' 3kg.

For whips, I once made the argument that a whip was composed of intertwined monofilament wires, resulting in an uneven surface of what for all intents and purposes are razor-sharp threads.

Pneumatic maul, adamantium laced staff...

The simple addition of mono edged spikes? Or mono edged serration like the surface of a meat tenderising mallet (they hurt a lot.)

Or course you can go as high or low tech as you want but sometimes I think the the simple things really are best.

For blunt weapons, I usually rule that a 'mono' upgrade equates to a depleted uranium core or other enhancement that increases impact.

DPU is maybe a bit much (especially as some of the fancier features only activate at very high impact).

What's wrong with the good only mercury-filled handle though? When you lift the weapon, the mercury runs to the hands meaning it's easy enough to wield, then when you swing it, the coriolis effect moves the mercury to the head/impact area of the weapon, making for a harder impact.

I generally have said it's just made out of high-impact alloys or something. Some future unobtanium that nonetheless is not as cool as a power sword or adamantium.

A high tech regiment might have access to all kinds of special weighting systems or gravity manipulators etc whereas a feral world mono upgrade would likely consist of a bunch of spikes attached to the weapon.

In DH there's a good explanation for non primitive baton in one of the books. It says that it has a holo chamber running along the inside of with free floating heavy weight that adds to the impact. That could be some super heavy material like depleted uranium, tungsten or some heavy liquid, like mercury that can flow around internal channels.

What reinforcing impact surfaces with super hard / super heavy materials like adamantium or carbide. Or even sci-fi materials that amplify impact.

Perhaps with scientifically angled surfaces to maximize pressure.

Perhaps it uses low grade energy field to reinforce the impact. Or force emitters / small jets that that fire off to speed the weapon forward.

Or some combination of those.

When I read "scientifically angled surfaces to maximize pressure," I think that's a funny way of saying "a cutting edge."

I always assumed it would be a low level power field, though one of my players once decided that the reason why his two handed warhammer had the effect of mono was because it basically had a rocket motor in the head that activated when swung giving him a super smash effect......

For hammers we had two ways to go.

Either it was a weapon like a bec de corbin that actually had a pointy end that got improved by mono the regular way. The other option was some sort of pneumo shock where additionally force would be applied mechanically.

Even a tapered head that concentrates force without being actually sharp will greatly amplify the impact force delivered. (Think; Ball-peen hammer!)