I was under the assumption that you become the mayor at the end of the prologue, not Act I. Either way, this is an amusing oversight seeing as sandbox mode removes the story. It's a shame seeing as that questline ends with Cali getting her own personal weapon (the first one available as far as I can tell) even if it doesn't stand out much in terms of stats. Perhaps reputation points would be a good replacement for sandbox mode considering the whole "you need more reputation" hint.