Something I'd personally do is look at the huge amount ODI cricket is being played, as compared to Tests. So I'd impose guidelines such as:
No bilateral series comprised solely of ODIs
A minimum of three Tests to be played every series

And also the amount of cricket being played in general. So:
A maximum of four series to be played by each country in a calender year (because less is more, right?)
At least two warm-up games before the first match of a tour

And the real biggie:
The Champions Trophy to be abolished. The World Cup and the T20 World Cup are enough, aren't they?