Just painting Egyptian and Hittite Armies what Size of bases for chariots  do people suggest ??

Like the question on basing Romans, it comes down to what rules you are using, your abstraction level and in this case what function do you see the chariots performing?

In most rulesets for the ancient period the frontage of a base is normally kept the same to enable melee calculation processes to work easily. So, probably keep the same frontage as other types but vary the density according to function and however many you can practically fit on.

I'm curently working my way through a huge pile of tin to create a full 1 figure to 1 legionary, plus cavalry and impedimenta (pack mules, supply carts, soters wagons etc) and that will probably take up something like an eight seat dining room table. Probably not the wieldiest layout for table top wargames, the enemy troops would need to be on another table in the room! 

A few years back when visiting a museum in Lincoln (UK), there was a 1-to-1 representation of a legion marching out from its fortress. The figures were all 25mm. So, it is possible Peter!