Thats an excellent plan and many people have already suggested it... BUT MOVING THE CHIMERAS 12 ALSO STOPS ME FROM FIRING BACK!?!
This has to be done with some strategy in mind.
Not moving at all give the Orks auto-hits in close-combat and basically hands them your tank. Moving 6" makes the Orks hit you on 4's (a 50% threat reduction), and moving 12" makes them hit you on 6's (an 83% threat reduction).
Often, it's best to move your Chimeras forward 12" (and pop smoke) on the first turn, so you can move 6" on turn 2 and engage them with the heavy flamers you're packing. If you need to pop trucks on turn 1, just move your Chimeras 6"
Your Russes should ALWAYS ALWAYS ALWAYS be moving too. So take the sponsons off. Demolishers have rear armor 11, making them pretty much impervious to anything but a power klaw. Put a heavy flamer on the front of it too. Often this will kill more Orks than the Demolisher cannon!
Russes can also be used to block loota-fire that can kill your Chimeras and Hellhounds.
Hellhounds should always be moving at least 7" no matter what. This still lets you fire the Inferno Cannon. Taking this tank down will be the Ork player's #1 priority, so make it as hard as possible so you can take advantage of the distraction it provides. Charge it into their midst, forcing them to bunch up and attack it. They should do little, if any, damage to you in close-combat. Then you simply back up and flame away at the tightly packed mass. If you keep some Chimeras or a Demolisher nearby they can have some fun too.