And to allow places to be open on the Sabbath? Where is the line drawn? Is a religious mayor supposed to watch Jerusalem turn into a Haredi city and do nothing?

To the question I was asked, I wrote that there is a halakhic prohibition against desecrating the Sabbath. I didn’t write what should be done in practice. That is not a halakhic question. If it is forbidden to initiate activities, then it is also forbidden to run such activities for residents. That is the halakhic consideration. And if you are bringing in considerations beyond Jewish law, then this is not a halakhic question.

I am bringing in other considerations. I think Jerusalem becoming a Haredi city is something that needs to be prevented, and it could have serious consequences. But in the end I want to remain within the framework of Jewish law and not do something forbidden. I didn’t think it was permitted to desecrate the Sabbath.

It is not permitted to desecrate the Sabbath. There is room outside the halakhic framework for policy considerations, mainly regarding the question of how much to intervene in Sabbath desecration. Nobody is talking about you yourself desecrating the Sabbath.

It’s a shame to waste the effort, because Jerusalem will end up a Haredi/religious city eventually; the only question is when.
That is because the classic secular person in the postmodern era has nothing deep-rooted tying him to some ancient Middle Eastern city. The same is true of this region of the country: there is nothing tying him to it other than the fact that he was born and raised there, and that this is the mentality and language he knows.
(There are of course some with national and traditional feelings, but they are becoming fewer and fewer. What can you do—these days it’s not the trend.)