Support of stereo mode without IMU?

Although ICE BA is designed for VIO, is it possible to run without IMU? This has a wider application,like stereo camera rigs and RGBD camera (depth could be converted to stereo mode).

Start by tracing ICE-BA's VIO and IMU assumptions, then review how stereo camera rigs and RGBD depth converted to stereo would fit. Done means establishing whether IMU-free operation is supported and, if so, defining and implementing the required stereo/RGBD scope.

Written by the indexing model from the issue text.