It would be a very cluttered map. Note there is no map-mode showing the positions of the three factory types even in general play, you have to select each state individually, or use the construction interface to get an overview.
That's why, in my opinion, a good solution would be to allow switching between at least 3 map modes within the actual peace conference interface. The first mode being the exact same as it is now, showing the point cost of acquiring each state; the second mode being functionally identical to the current resource distribution map mode; and the third mode showing the industry in each state.
This way, neither the 2nd nor the 3rd mode ever needs to have more than 5 visible pieces of information per state, which is something that has already been made to fit for the resource map mode (since synthetic plant outputs are displayed on the resource map, it is certainly possible for a state to produce a little bit of each of the 5 resource types). The industry map mode, in my mind, only needs 5 pieces of information as well - number of civilian factories, military factories, dockyards, rocket sites, and nuclear reactors. The key info for synthetic refineries is already present in the resource map mode, and I think number of empty factory slots would be fine to leave in the tooltip the player sees while hovering over the state.
I do think that a general map mode showing the industry would be a helpful thing to add long term, in any event.