Like the picturephone, this is a bad idea that refuses to die.

Unless you meet the child age requirements, you won't get a DISCOUNT for weighing below average. For really, really small aircraft they have to do it (I once flew on a 6-seater from Manila to Caticlan that was like that). For most aircraft including RJs, though, they don't have to.

The fundamental problem with this line of reasoning is the implicit presumption that the other party your dealing with is fair and dealing in good faith. I suggest you re-evaluate that when it comes to airlines, which have had in their history such practices as training phone agents not to quote the lowest fare, imposing "fuel surcharges" and not backing off when fuel prices drop, or charging $400 for a non-competitive 100-mile route vs. $99 for a competitive one to go all the way across the continent. And charging $250 plus fare difference to change an international ticket.

Their take would be, "Wow, maybe there'd be consumer acceptance of charging by weight. Let's try doing that AND this other invented fee we were planning to introduce."

You're acting like Elin Nordegren when they're Tiger Woods.