Allow measure numbers to appear below the staff
As the title says, allow placement of measure numbers below the staff instead of above it.
Two cases here, one is the simpler "all measure numbers appear below the staff", which could be a setting in the style. The second case is "allow the user to set 'measure number below the staff' for individual measures", for example to avoid a particular rehearsal marking.
This can help avoid collisions with rehearsal markings, although it raises the possibility of collisions with below-the-staff elements. As this would be user-configurable, and most elements can be adjusted manually anyway, I don't think it would be a huge problem.