When two hyenas fight there is no agreement possible. Ripple and the SEC are two beasts, giants who want to be right and not give in. For money, for reputation, there are many reasons that we could mention in this thread. Burning a percentage of the XRP supply could be considered a defeat by the community (although I personally think it would be a positive) and that could drive the price down.
For its part, the SEC has all the instruments (not just money) to put pressure until it tries to find the weak point, no matter how small, to bleed the rival hyena. But looking at it from your point of view, if Ripple and the SEC could reach a deal, I don't think it would have anything to do with burning a portion of the XRP supply.