Unless you get some special waders with 40 pound weights inside of them your waders will not make you go down. Waders protect you for water, that is it.
We are not talking river or stream, different scenario.
If you fill up your waders with water then you might have a hard time getting back onto your yak. A wader belt easily prevents this.
Don't over think this stuff
Here is another brilliant idea. ( free )
Wear your Pfd!