Can I generate a grid navmesh that has the exact same number of points as my map (a 256 x 256 map would generate a 256 x 256 navmesh grid), and then be able to call those points directly by index number? Possibly even run-time manipulate their cost values / walkability? (for instance if a nation closes its borders, set all points on navmesh to unwalkable)
Asked a different way: can I give the nodes penalty values based on their world location? If not that, Can I create a complete grid (no holes) and then edit the node values (movement penalty, can not traverse) via node index numbers or 2d array coordinates?
answer found 
and it is of course
https://arongranberg.com/astar/docs/graphupdates.html
more good:
https://arongranberg.com/astar/docs/usingnodes.html#node-properties