Hi carsz,
I usually try to avoid large Production Orders, it gives a lot of pains with month closing processes, costing, capacity and so on..
I would suggest to set a batch qty (in site specific order settings) related with actual production flow (if capacity is 250 by week maybe it would be 50..).
Of course you are going to have more production orders but if the batch numbers are accurate, the production orders can be managed in a natural way in the production plant. I have had several implementations where I set the batch number to 1 and it worked smoothly :)
In order to give more sense to the production orders you can also set the sub-assembly items in the BOM with line type=pegged supply and then you will have all the production orders tree linked.
But focusing in your example, there is a functionality called overlap, but I know it to overlap operations not sure about production orders. I think this link can be very helpful:
http://blogs.msdn.com/b/axmfg/archive/2013/05/28/working-with-overlap-in-microsoft-dynamics-ax.aspx
I hope this helps!
Carlos B.