You should probably render using a 6-pack camera setup.
Rendering with a spherical camera is more convenient but unfortunately a lot less efficient to render (you compute a lot of pixels for very distorted parts).
Here is a camera I use for this kind of situation
cubeMap_camera.tgcThis is a simple camera with a 90 degrees FOV, animated to rotate from frame 1001 to 1006.
You can move it to the position you like. What you only need is a renderer (don't forget to put a GI prepass padding to something like 0.1 and turn off motion blur) then render the 6 frames. You can stitch them back in Nuke or Photoshop.
This way you can render a much higher resolution panorama, and you can even split the renders between different machines. I also recommend you use a GI cache to be sure the edges of the images matche perfectly.
Let me know if you need any further help on this, good luck!