The idea of a plant will last as long as the suspects surround the case. no matter what comes into play about them they will continue to try and prove that suspect. even when the witnesses have seen these suspects. a plant makes there suspect thrive. a plant proves Cooper made it. they go hand in hand.
IMO, Cooper would have had to of known about Tina bar, the erosion, the amount of people who visited the beach. it just doesn't make sense. how could he have known the money would be found, or that it could weaken his trail? the money would have to be found early in the investigation to throw them off his trail. how do you bury something thinking that? they have never been on his trail. how would he have known they would turn the money in, and not keep it? that almost happened! nothing adds up. if the intention was for the money to be found, why wasn't it protected? the "master plan" didn't include this?
Christiansen, Weber, Rackstraw, and many others all rely on a plant. it's a must, a need. don't tell me Tina has never seen these people, or the passengers...what dark hole do they think these people live in. it's as ridiculous as the plant.