Automating the master channel (down)?

[Switchcraft]

My understanding is this.
the mix bus of PT HD has a 48bit fixed limit and Logic has a 32 float limit.

This level of bit depth accounts for a much larger dynamic range than any converter can handle.
So, if you have a mix that is clipping the master fader, pulling down the master fader will simply bring down the level that is not internally clipping the mix buss, but has a dynamic level to high to be output to your converters.

Obviously, this is thought of as bad practice, but I have one track that has about 6 different songs within it. It is a bit of a schizophrenic intro to an album. The beat keeps jumping around in different styles, tempos etc. The first one beat is very low and then by the time it gets to the last arrangement I need to pull the fader down to about -3.0 dB to keep the MC from clipping.

So, would automating this change through the song (in steps as each beat comes in, it will be unnoticeable) do anything adverse to my mix bus.
I did it and it sounds great, so if it sounds good, it is good, but I just want to see what others think.

Sidenote:
A platinum selling engineer I know has a take on this.

He says he always starts with his ITB master fader down about 3db and pushes his track channels hotter to utilize the greatest dynamic range of each channel. When these sum to the master channel they are again using the most of the bit depth of the master channel. Pull down the master channel is basically allowing the converters to produce that mix. So, he says that you are using all of the dynamic range of your tracks and master channel.

Obviously, this is only ITB and there will be plenty who disagree, but I have found it to be useful way to mix. OTB is exactly the opposite.