The European billhook has been made in many hundreds of shapes, each one specific to a task, a user or a region.... Convex, straight or concave - single or double edged, with or without a back hook etc...
Blade lengths vary from 6" (e.g. a spar hook for cutting thatcher's spars) to 12" - but the most common are 8" or 9" long - with a 6" handle..
Typically they weigh from 600gr to 1kg (approx 1.5 to 2.2 lbs) - most were forged to thickness and shape, and typically can be 3/8" at the tang, tapering to about 1/8" at the nose along the back, and also tapering towards the cutting edge...
This design looks very like an English Hertfordshire pattern, with the back blade also sharpened (on the English hook it is blunt, and used as a hook to draw the wood towards the user) - however even then there was no fixed design, and it varied in shape from maker to maker, with some having a straight blade rather than a convex one...
Many English and French patterns came about as 'specials' ordered by someone to meet his(her) requirements - so this design follows in that tradition... Personally I would prefer a tanged version with a turned handle, as on English and French billhooks, but the rivetted scale design is common on Italian ones, as well as machetes and cane knives..
Go for it - try it and see what it feels like.... If you only want a thin blade, an old crosscut saw is made from steel about 1/8" thick - thicker than many machete blades... Saw steel is usually silver steel, with a high carbon content and tempered to a spring temper - ideal for small billhooks, or even knive blades....