Subfloor :(

I'm not all that enamored of the subfloor I have to work with. It was laid for the tiling techniques of the 50's, and I do not plan to try those techniques.  A few thing to notice in the picture below:

• Traditional subfloor with gappy diagonal boards.
• Thinset drips through the slats into the laundry room.
• Not strong enough to support tile by itself.  Notice the hole where I knocked out a knot while pulling up the parquet?  There is another place under the tub where bad grain gave way when I put the foot of the ladder on it.
• Lowered subfloor where they originally had tile.  That was to accommodate the 2" thick mortar bed under the original tile.
• I don't want to put down 2" of mortar.
• Those boards are not even nailed down!  The are just loosely laid in (notice the gap by the wall) in the very reasonable expectation that the mortar will hold them in place.

I can't just put something on top of those diagonal boards.  I am already worried that the tile floor will be too high.  I'm going to have to pull them out and replace them with plywood.  That task is complicated somewhat by the fact that the walls are sitting on top of them.  One thing I have going for me is that I don't have to go all the way to the left or right walls since I will be putting cabinets there.

I figure I will also pull up the loose boards in the back section, clean the rubble from underneath, and use several sheets of plywood to bring that section up level with the front part.  Should be a fun day tomorrow.  At least it won't involve tile, sheetrock, or insulation dust.