Flooring Tile - tiling archway above shower in bathroom

I have an archway above my shower that is currently tiled, I will be remodeling my bathroom soon and plan to remove the tile. I am sure under the tile the substrate is screen and plaster (1927 built home), I want to maintain the arch but replace the tile, and I am sure when I remove the current tile some sections of the current substrate will crumble and come apart. What do I need to do to replace the current substrate and still maintain the arch or how can I repair the damaged sections of the substrate and still have an adequate tile application that wont degrade?

if the wood under the tile is rotten you can take a peice of luan 1/4 plywood and bend it to get the arch then cover with durock the 2x4's under the plywood that is already there should still be ok they are already cut to form the arch all you have to do is finish it off and add something for the tile to stick to:cool:

Is there flexible Durock that I could bend to the form of the arch or do I have to score the Durock sequentially (distance between scores is the width of the tile) so it will flex to the profile of the arch?

you can flex the rock to do pretty much what you want it to do

Excellent, thankyou very much. This will be an interesting project, I have not had the opportunity as of yet to work with Durock, but I have doen extensive drywall work.