Rather than roll (N * 5)d6, why not just roll Nd(6^5)? That is, for each Diceware word, pick a random line in the wordfile. This is not a true simulation of Diceware, but for correctly dimensioned wordlists, one could explain any 1d(6^5) die roll as a 5d6 die roll by drawing the dice e.g. as in #8.

The advantage is that fewer random numbers are generated and that this method works for wordlists that are not well-formed. I.e., you can still draw words uniformly even when you are unable to express the word's position in the wordlist as a 5d6 roll.