CHeck with your AHJ as to his feeling of whether it will be subject to phsical damage. I have called for a meeting on a few occasions to get his/her feel for what I wanted, or what would be acceptable. Personally, it looks like there is enough of a lip coming off that step that a rigid conduit would not be affected (an LL or LR can keep you tight in the corner, but I don't know off the top of my head if that is an acceptable location for a condulet). You have weather/puddling issues as to how well a metal conduit would hold up over time, if that is an issue, will NMRC hold up to traffic over time, etc.? I think your install idea is a good start, but "subject to physical damage" can be very subjective.