Hi there ajmena,
It is worth noting that signal strength is not directly proportional to quality or accuracy of the measurements. Although there is often a strong correlation. You can read more about that here. If your aren't doing so already, I'd recommend you check your application to see if the position data is actually inaccurate before discarding low signal strength readings.
Changing the motor speed to 0.5Hz
The sensor does not currently support motor speeds < 1Hz. That likely won't change, as updating motor behavior can not be accomplished through a firmware flash. Therefore, releasing new devices with support for slower motor speed would bifurcate the existing product/software support.
Doing two scans and combine
You can always perform multiple scans and combine them later. However, unless the sensor remains incredibly stationary, this might introduce more inaccuracies in the final merge than a 1000Hz scan would have presented in the first place.
Changing the rotation speed.
I assume you are referring to the rotation speed of the 3D scanner base? This would be the easiest solution. Currently the scanner matches the movement of the base to produce scans with roughly similar yaw and pitch angular resolutions. See here. If your application can deal with a longer scan duration, you could simply increase the resolution of the base movements such that the spherical scan is composed of more 2D slices.
Currently the base rotates 1 step for each sweep rotation. You could modify the scan process to perform 2 x sweep rotations (2D scans) for each movement of the base. This modification applied to a 1Hz/500Hz setting would then produce similar resolution scans to a 1Hz/1000Hz setting without the modification. The downside would be doubling the duration of the scan, but the upside would be signal strength values from a 500Hz sample rate.
You can prototype all of these modifications rapidly using the dummy scanner on your local machine. See here.
Hope that helps!