Jeff, I just read your advice again
2. Export your 1080p50 footage from Sony or Ae as 1080i25, which is also a BD-legal frame size/frame rate combination.
Choice #2 should work well because the exported frame rate is exactly half of the source frame rate and is easily converted to interlaced by most decent editing and SFX programs. The reason for that is that the editing program has 2 full frames of 50 fps video information from which to build 1 new full frame of 25 fps video. No interpolation required. So even if your 50p video contains cross-frame motion that might seem choppy at 25p, it should look pretty good at 50i.
so first you suggest to downscale to 1080i25 and then you talk about 1080i50 – do I miss something?