Well, you do not need a separte stream option really for 3D Blu Ray - for 3D Blu Ray you need the Sony AVC/MVC encoder, and have to choose and modity the MVC templates (see below).
To maintain the resolution and quality of TD10 footage - no easy task at all for 3D Blu Rays. Typically, the TD 10 footage is 1080 50i (PAL areas) or 1080 60i (NTSC areas), but not 1080 24p. Unfortunately, the 3D Blu Ray specification foresees 720 50p, 720 60 and 1080 24p as MVC only. So for 3D Blu Ray you have to convert the TD10 footage, and that will reduce quality and/or resolution! There is no way to avoid that really, there is the only way to try to minimise the quality loss.
Generally spoken, there are two routes: first you could try to convert the footage to 1080 24p, by rendering the 3D footage with the Sony AVC/MVC encoder to 1080 24p. Choosing that path will remain resolution, but it will interpolates every frame new - what is something that reduces quality really. Many people have not been very happy with that way, and there is not really a good way from native 1080 60i to 1080 24p.
The second way would be to render to 720 50p (from 1080 50i camcorders) or 720 60p (from 1080 60i camcorders), what works better. That requires a good interlacer - and the Vegas internal deinterlacer is of medium quality only (some people tend to use deinterlacing plugins like the Yadif plugin). That is the better way, since not every frame must be interpolated, even if it requires the software to deinterlace the footage and resize it what will cost some quality. If you wish to be bettern then Vegas can do, you could use AVIsynth to deinterlace to 1080 60p, then scale to 720 60p.
If you give that try in Vegas, make sure that you set deinterlacing to "blend" or "interpolate" in the project properties, but not "none".
Be aware that the MVC templates in VMS r247 in the Sony AVC/MVC should be changed by using the customization buttom - take the MVC 1280x760 60p template if you use the NTSC model, but change the bit rate from 10 to 25.000.000. If you use the PAL model, you have to change both the bit rate to 25.000.000, but also the frame rate to 50 (double PAL). I recommend you to save the new templates for the future.