Guys bid sniping at straight time is a September and February problem. I just picked up a straight time leg for the first time in almost a year. It pained me to do it, believe me.
I know the seniority system sucks, but it is the same here as anywhere else.
Also, the problem with your scenario is that the guy bidding straight time over the cap would have gotten the trip after the new guy bidding straight time under the cap. KTC.