I have spend some time to investigate Win64 debugging issue. After some googling and some testing, I have verified that while you can start 64 bit app from 32 bit, you cannot start it in this way with debug flag. All other combinations seem to be allowed.
Which, to sum it up, means that it will not be possible to do Win64 debugging from Win32 ide.
Well, Win64 debugging in Win64 ide still does not really work well, but at least it can be started
My current conclusion is that in order to support this, we will have to have two Windows installers or maybe one that will install either 32bit or 64bit theide.