Ask for advice on cross-platform design?

Question

Software design

All the best!
We will be making an existing MFC application cross-platform (along with porting the GUI to WebKit). The project is large, there is no experience of such a large-scale refactoring. But the overall picture is emerging, especially thanks to the comment of the habrauser nick0x01 , which put everything on the shelves.
To minimize the number of #ifdef PLATFORM, all platform-specific code is placed in separate files. Factory methods create objects for a given platform (GoF has cross-platform examples in an abstract factory, but this seems to be a matter of taste). Everything is beautiful, but did not forget anything? Do you have anything to add to this simple scheme? Any comments from experience?
It is clear that “the eyes are afraid, the hands are doing”, but while the project is not yet in work, I would like to prepare as much as possible.

Answer 1

I'm sorry, but wasn't it easier to port everything to Qt? The amount of platform-dependent code would be reduced by several times, there is our own QtWebKit.

Answer 2

Kgm. Isn't it easier to move everything to the web? As far as I remember, MFC is heavily tied to many winapi goodies. And if your business logic is separated from the display, everything will be much simpler.
PS highly recommend Kendo UI and .NET MVC 4