As the guys on x360 said, this sort of thing isn't without precedent. GRAW had an achievement that required you to be #1 on the multiplayer leaderboards. Lips has two acheivements like that, world record score for one song, and top ten for twenty songs.
And yes, it becomes impossible to beat certain scores after a while. Unless Capcom decides to be merciful (ie, not retarded) and reset the times every week or so.
I just managed to get the world record for one of the training maps, after a couple of hours of grinding. And unfortunatly for all of us, the TOP TEN and NUMBER ONE titles are definitely part of the standard Noms de Guerre.
The record times were pretty turbulent while I was doing my runs, so it's still possible to edge out the world record holders, but the opportunities are shrinking fast, and apparently when the game is released in Japan, the rest of us will be pretty much screwed, as they're big fans of Lost Planet.
There are 50 maps to get a record on. So it's not impossible...just insane....Two things that might help:
1. The fastest route will involve well planned and accurate grappling.
2. Try to minimize the height at which you fall or jump from, because the resulting stumble slows you down about half a second.
When grappling up onto things, try to grapple high on the block, so the leap up catapults you slightly forward, which gives you about 0.2 of a second.
Also, don't restart a run if you're a little behind at your first checkpoint. On my world record run, I was about 0.3 of a second behind at the first checkpoint, but managed to jump ahead 0.4 of a second by the second checkpoint. Which means, for that matter, map 5-2 of the basic courses still has room for improvement if anyone is interested :P
So yeah, whoever is going for the plat, DO THIS ASAP, because it's only going to get harder the longer you leave it.