Would a leaf shape be good for a dagger blade and is there historical precedence for this?

Specifically a double-edged profile? Then yes Leaf blades are quite good in the ability to provide weight at the cut without adding extensive mass to the weapon/tool. By thinning the weak of a profile but moving the mass forwards gives the weapon more bite at the cost of some versatility.

These right?
We have 3 precedences from history to share at the moment.
First is the Pugio dagger from Roman antiquity.

Gurka Khukuri. Have been known to bear a distinct leaf blade. As many were/are double-edged at the forward portion.

Then there’s the Greek Xiphos sword. Which was a smallish thrusting sword. Routinely made of bronze then later of early soft iron. This made a thicker blade wiser than thinner less shapely profiles.

There’s also spear blades from Gaul and Germania. Arrowheads from China and similarly the use of naped stone from the Americas.
The leaf profile is exceptionally robust and sturdy. If damaged honing it down preserves the weapons function without losing too much of it. Retaining the value and negating any need for an immediate replacement that straight or curved profiles sometimes suffer.

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