Cool. There's a third option that you might want to consider for winpty. (I was experimenting with it before I left Microsoft.)
The basic idea is to use a DLL shim to provide your own console API implementation for a process and its children --- you can replace the system console API with your own by shimming DLL import and export tables. You'd use your own type of pseudohandle for your fake console handles; programs written to work with the old console pseudohandles should work correctly with your pseudohandles, provided you've hooked the relevant HANDLE-using APIs.
Cool. There's a third option that you might want to consider for winpty. (I was experimenting with it before I left Microsoft.)
The basic idea is to use a DLL shim to provide your own console API implementation for a process and its children --- you can replace the system console API with your own by shimming DLL import and export tables. You'd use your own type of pseudohandle for your fake console handles; programs written to work with the old console pseudohandles should work correctly with your pseudohandles, provided you've hooked the relevant HANDLE-using APIs.