I too had this same requirement from client. Client wanted Edit Feature Attributes Page to be displayed side-by-side with Map page and not exclusive to each other. I started looking into an option of creating a custom page with Map control and Edit Attributes but had technical difficulties. I also played with the idea of showing a floating WinForm for Edit Attributes but it required lot of coding. Client has temporarily accepted out of the box solution of either map page or attribute page and but will require this sorted in the next phase of the project.
Cheers,
Vish