Speaking about player interaction, how social progress diffusion would be handled?
i.e. as far as I have read, if you do X your nation becomes better at X and thus social progress is unlocked for X category.
BUT what happens for the other categories? Is there some catch-up mechanism?
One problem I see is indirect snowball effects. If you focus on military category you become better than the rest on military aspects. Ok.
BUT there should be a minimum social progress at other categories even if you do nothing at them, otherwise some playstyles will be indirectly handicapped due to not having access to specific advancements (professions? Units? promotions?).
Also social progress without diffusion, minimum points production per turn and a way to unlock them at specific years (or just adjust the minimum points to account for this) may also impose a double penalization. You are already spending -indirectly- production and resources to focus on a category, but I suppose specific categories will improve production and resources... so it would be counterproductive to focus on non-production categories... since that way you will be reducing your economic system now AND reducing your possibility to improve it on the future.
Since the premise was to give options to players, some thought must be put on this... otherwise it will just become another layer of complexity without real choices. It would be simply better to first focus on production to then expand the other categories, instead of a decision to made according to the context.
Europa Universalis (maybe Stellaris is the same) has a similar Social progress system for 4 or 5 categories which unlock units, buildings, etc. Thing is level cost is reduced every year, and nations of your same culture further reduce the cost. At some point you simply advance on every category no matter what you do. But you can focus on one of them by spending income... (applied to Col, it would be spending production creating units, time exploring, whatever...).