As awesome as LBP was, its sales were not. Sony's priority should be on making a new killer-app game, a la Wii Sports, not retrofitting old games that didn't meet sales expectations with the control scheme.
If you could 'retrofit' an old game and make it a $20 download, it might be worth the effort. Perhaps neuter it enough so the cheap version is not playable with a regular controller.
I also think Sony should court every decent third party Wii game developer that didn't have successful sales on the Wii and encourage them to migrate their games to the PS3. If sales were poor on the Wii and more viable on the PS3, then there might be a steady migration or at least viable dual platform development.