Hello Tom,
Sorry for the late reply. You might have already received the reply via e-mail, but the case may be also interesting to others.
It is safe to swap if the number of bands is the same. PhotoScan doesn’t store information image bit depth (8 bit, 16 bit, 32 bit, integer of float) so, for example, 8 bit images can be swapped with 16 bit images at any time.
Swapping the images with the different number of bands is more complicated, because PhotoScan loads the list of bands when the images are added to the project and stores them in the project file. So besides swapping the images themselves it is required to update the list of bands in the project itself. This can be done using a Python script in PhotoScan Pro.
For example, assuming there is only one sensor (calibration group) in the project, you can change the list of bands by executing the following line in Console pane (or in the script):
PhotoScan.app.document.chunk.sensors[0].bands = ['Band 1', 'Band 2', 'Band 3', 'Band 4']
The number of bands and their names can be changed as needed.