Hi Allan,
I believe that some other people have used their own switches and done as you say. However, there are two downsides to consider, one is the loss of the LED which can be useful to indicate the state of the automation and the other is that "normal" switches with an on and off (up and down) position can also cause confusion. Retractive switches (momentary push) make more sense. Cortex can cope with either, it is more a question of confusion for occupants.
I recall reading of someone else's encounter with building control over the low position of electrical accys. You should enter a discussion with the inspector, but perhaps one way round this is to make it clear that the DFP is an informational device and clearly needs to be at comfortable eye level. The reg's clearly have been written to ensure accessibility for wheelchair-bound people, but didn't anticipate the growth of devices like the DFP. If you have an auxiliary light switch under the DFP at the correct height perhaps that will help. Or you could point out that your HA plans are far more accessible to a wheelchair bound person since they could operate everything with a remote control.