Kitchen Makeover.....ceramic tile questions!

I have a kitchen makeover thread going on over in the home decorating forum. We need the advice of a tile guy or girl!!

We have major problems with the ceramic floor tiling project----We have hit a clitch. The top layer of plywood is 5/8 inch plywood. The cabinets and wood trim and everything was put down on top of it when the house was built. We were expecting something like 1/4 plywood on top of the subfloor. That way we would tear it up, put cement board down and than ceramic tile on top. If we tile on top of the 5/8 plywood it might raise the appliances up to high to fit under counters and such!!!! I also don't know if tile would stick to the floor after the old glue is scraped away. I also think ripping out plywood that is this thick is going to be impossible--too difficult to remove because the cabinets sit on top and the door trim sits on top. I'm wondering if we can tile right over the top layer of plywood? Wouldn't the ceramic tile crack without cement board under it? What a mess....... Anyone have any suggestions?