Well, this could be easily done. Unfortunately, I'm on a seminar, so I can't write anything, but it might be integrated into the LOD core as well. You know, in GTA high res building models and low res building models are visible the same time when they blend. So, your routine has to recognize the change (over str_for_entfile for example or the LOD ranges) and immediately after this the high res model has been changed to the low res one by A6. To achieve this effect we need to reload the high res one and fade that out (or in). During the blend process we got more polygons than it should be, but it looks nice. When I come home during this week,, I will try to write a routine like that (this topic awaked my interest )

ciao
-Christian