Thanks to the flexibility of our Couatl scripting engine, there's no need for any scenery update or remake.
Most of the object loading ranges are already controlled by the "Anti pop-up" setting, which in P3D V4 by default is at its maximum value, which means you should see a far bigger loading range compared to 32 bit versions. Have you maybe lowered the setting ?
If it's already at the maximum value, could you please make an example of an object that appears too late ? Perhaps there's still something specific on those sceneries that is not controlled by the Anti pop-up, so it might be possible to fix it easily without making larger changes to the scenery.