Getting PhD in an adjacent field I plan to pursue
Would getting a PhD in operational research immediately preclude me from tenure track position in Math, CS and Philosophy Departments? Even if I have a solid amount of publications?


It would not preclude you from applying, but your success would depend on whether your research profile matches the position as you would be competing with many candidates who might be a better match. The number of publications is important but it's not the most important criterion.


  If so, would already having a PhD hurt me if I applied for admission to a PhD program in Math, CS or philosophy?


I can't see any reason why already having a PhD in OR would decrease your chances to get admitted for another PhD program later. But will you still be motivated for that after getting your first PhD? 

An alternative option would be to progressively switch topics after the PhD through one or two postdoc contracts.