Absolutely:
I don't understand why you keep calling the Lydiard's idea "multi-tire"--speed development, drills, hill exercises, etc. to develop fine speed? Ah, is it because "multi-tire" doesn't emphasise good aerobic development with lots of jogging "at the same time"?
In regards to the swimmers; my understanding is that they do tons of swimming. Technique work, yes; but what about their spending hours and hours in the pool swimming? Particularly swimming needs good aerobic development because even their "sprinting" takes close to 50 seconds. You know the Australian national swimming coach, Dave Wright (I believe was his name...), and Lydiard co-authored a bood called "Swim to the Top"? As I understand it, Ian Thorpe employs this principles.
In regards to coming down the distance; that's what Nakamura suggested--run the marathon first and come down. El G used to compete in 5000m as a junior; Seb Coe used to run a lot of XC races as a youngster; Radcliff dramatically improved her 10000m time after she started running the marathon; Yoko Shibui setting the national record in 10000 (beating Deena Kaster) after starting running the marathon; Dick Quax improving his 1500 PR by 3 seconds after moving up to the 5000m... On the side note; Mike Stember failing to improve his PR in 1500 after "sharpening his speed" by running lots of 800m (and turning fairly decent times as well)...