Let $S$ denote a keyless permutation that operates on $4$-bit inputs and returns $4$-bit outputs (that is, $S$ is a $4$-bit S-Box).
In this question, $x_0$ denotes an arbitrary bitstring that ends with 0000
(four zero bits) such that the length $L$ of $x_0$ is a multiple of $4$ and there is no upper bound for $L$. Then $x_0 + i$ denotes a bitstring that represents the sum of $x_0$ and $i$, assuming that $x_0$ is interpreted as a single natural number and all ($L - 4$) leading bits of $x_0$ are not affected. For example,
000001010000 + 1 = 000001010001,
000001010000 + 14 = 000001011110,
000001010000 + 15 = 000001011111
Does there exist an efficient iterative construction $F(x)$ based on $S$ so that the length of $F(x)$ is $4$ and a tuple $$\{F(x_0), F(x_0 + 1), \ldots, F(x_0 + 14), F(x_0 + 15)\}$$ is a sequence of $16$ different $4$-bit elements for any $x_0$ (that is, each $x_0$ generates a permutation of $4$-bit values), and all of the $2^4! = 20922789888000$ possible permutations are equiprobable if $x_0$ is a sequence of random bits followed by four zero bits (assuming that the length of $x_0$ is $4n$, where $n$ is an arbitrarily large natural number greater than $1$)? If it is not possible for all permutations to be absolutely equiprobable in the mathematical sense, then at least the distribution of permutations must be as uniform as possible and look “pseudo-random”.