[>BKA< T Wrecks]

Hm, I see. Yes, that would make sense. After all, they are supposed to stand still in an elevator cabin until they have reached the corresponding WP on the other level.
Ok, this also means that accidentally flagging a normal waypoint somewhere in the street as a lift will cause problems, or at least inconveniences.
Bearing this in mind, the lift flag should be visualized somehow indeed. There are basically 2 options to choose from:
a) yet another waypoint colour (inappropriate IMHO, as the lift flag doesn't change the waypoint type and had better not do so. On the other hand, what are the odds that you will place a team-specific or camp WP in an elevator cabin? Rescue, goal and ladder don't make sense in the first place)
b) some little cross on a waypoint, like nohostage and button flags. Yes, maybe something orange, yellow (could be bad to see), magenta or purple? How about magenta, just like ladder WPs? You'll never use a lift flag on a ladder WP (unless you are either nuts or a moron or both), and the colour is already used and seems to work ok in terms of visibility.