I am a great believer in the right tool forr the right job, but I also do appreciate versatility.
If you are looking for more capability in your field camera, would it make sense to minimize the constraint imposed by the portrait requirement? Not certain what the 8x10 Ritter goes for , but having seen one, it seems like a nice camera. The one I saw was set up to take standard Sinar / Horseman boards.
If you are doing portraits in a studio, then a dedicated portrait camera with really big lensboards (versus your Kodak 6x6, or the smaller Sinar ones), able to take a massive Packard shutter and big lenses, and with lots of bellows draw might be a good and economical solution. They do tend to go cheap.
If however, your portrait requirements are more location based, then please ignore the above suggestion...