I have installed your 4 sceneries and loading times are ... "normal": not very more time than before !
One trick that I have used to place buildings in cities where feature detection didn't work so well, was to select all roads and line either side of them with houses, with an argument that they would need to be within a certain distance of a "city". This fills in much of the map, but does require a lot of manual cleaning up and adjusting afterward. Worth a thought if you're having trouble with countries like Egypt.While Libya is still uploading, I would like to show the first pictures from Egypt today.
But there is one thing I must say beforehand: Even though I have made every effort to implement Egypt well, I must admit that I failed miserably.
The data basis was again clearly worse in Egypt than in the other states, and you can already see that on the pictures.