If anyone cheated they should be removed from any winnings but I feel this would be impossible to prove with absolute clarity.

Give foundation 60k and split the remaining 60k between contestants feels fair as it's impossible to say who cheated and who didn't?

Would everyone be happy to hand over their work for this to be used as the kind donators see fit?

Foundation wins, contestants win and donators have a wealth of design to use as they see fit.