So What if Mallet became an anti-mobility creep item?
Give it the following unique active: For the next five seconds your basic attacks Cripple targets for 2 seconds, disabling all flashes, dashes, and leaps. Using a flash, dash, or leap places this active on cooldown. (60 second cooldown).
It would be pretty sub-optimal on champions without dashes all over the place since using your combo would disable the active. But on someone like Olaf it would be a Godsend.
to SR in that case