[thaumasiotes]

> in the case of static languages, you may have created a deserialization format that always emits BigInts

I don't follow this one. If your language, static or otherwise, is capable of turning this JSON:

    "100"

into a string, and this:

    100

into a number of whatever type, then it's also capable of turning this hypothetical input:

    100

into one type of integer, and this:

    100000000000000000000000000000000000000000000000000000000

into another type of integer.