My advice would be to take one small aspect and finish that to the highest standard your team can. Pick off something like the control of fleets of ships or the trapping you mentioned that could be done in 6 months.
Make a game of that, get it published and then come back to big project expanding bit by bit. Reason I say this is not just to get something out the door but also to get money in the door. Projects of "a cultural significance" may be getting EU funding soon, they do in France already. Others on the forum will know more about this than I.
Also don’t underestimate the workload involved in your project even with an experienced team of full-timers I would peg it at well over 3 years work and that’s being conservative plus you need to think about the visual standard games will be at in 3 years time.
Best of luck though.