1. Please check if your specific iMac was designed to hold a Fusion drive. If it was, then, you can add an SSD without removing the Optical drive. iFixit can confirm with a teardown of your specific model or their dual-drive setup for this specific Mac.
2. If you plan to remove the Optical bay to add an SSD, installing Windows is a very painful exercise.
3. Your setup is possible. On the SSD, split it in half, without using CoreStorage, and install OS X and Windows, without the HDD in the mix. Once OS X and Windows work, add the HDD and Disk Utility to partition as you see fit. It is also possible to do this when both SSD/HDD are connected, but it requires some work in Terminal using diskutil cs resizestack. Please see OSX and Bootcamp discussion for some of my tests.
4. All my Macminis have a 256/512Gb SSD and a 1/1.5TB HDD with Bootcamp/Windows on the SSD. The HDD was too slow for Windows 7 boots. They al use similar configurations.