...and everyone else wil get less.
This just adds variance, no benefit at all (especially to miners who don't have multiple gigahashes lying around).
It could be done however in a "Jackpot" kinda way - you can set e.g. 10% of your mining income to go to the Jackpot and then if you find a block, you get the jackpot.
This is however simple gambling and can be done without mining too, more frequently and with better/higher bets and more control over the variance etc.
setting 10% of your mining income into the jackpot, would that be the same as take a few coin out of the 50btc ?