As you are talking about lanczos and blockbuster, I guess you are talking about "my" optimal scripts for avi->kvcd jobs.
They are optimal in a quite simple but somehow complicate way : to achieve the highest quality with as much details that is possible in the lowest size.
As you see there is 3 parts in this sentence. It's (more or less) easy to modify the script to enhance one or two of the parts but the "optimality" is in the whole three ones.
Do you understand ?
Note: "optimal" also means 'the best script found at this time". I mean that nothing is never freezed

.