Also, if someone can figure out a few common guesses on what word you'd assign a number (the Michael Jordan bulls jersey really stands out in this regard) then you lose one of the main advantages of this PEG system - that people don't know your words, as BIP39 wordlists are public for everyone to see.
I don't pick the numbers arbitrarily. The numbers are coming from the seed. Say the number I must associate with Jordan is 28 (it's not the actual number I'm using, 28 is just a random number I've just generated for illustration purpose), then I must chose a word that codes 28 in the major system.
28 is n + (v or f). So I can picture Michael Jordan handling a knife.