This seems to me a much better idea than Blending, but unfortunately I don't know any filter or program that can do it.The idea is: Blur the mice teeth where needed, instead of mixing (=blending) them with the other field. As you see the blur gets stronger in the direction of the old position.So interlacing is a way to display the nonmoving parts with full resolution and the moving parts with half resolution, but fluidly. But even as technology marches on and camcorders get better, you will want have 2 options: To record interlaced (= smoother motions) or non-interlaced (= higher vertical resolution).It's a very clever way to cut bandwidth without sacrificing much quality. It is true that cinema movies are filmed with 24 noninterlaced (=progressive) frames per second (thus about 2/2.5 times less than PAL/NTSC) and look fluid, but this has a special reason: How many frames can the human eye see? This gives you good results, when there's no movement, but results in unnatural low quality movements.You could even add an effect like this (Motion blur) This motion blur is done nowadays when you need to convert 50fps footage to 25fps footage (to make 50fps camcorder footage look more film-like).Or to make comics and rendering (like "Monsters Inc") look more film-like.
There aren't any motion interlace lines there, but this is a frame where there was a short flash, thus there's a difference from one field to the other.
To make things even more complicated, some digital camcorders have something you could call "color interlacing".