Curiously...

A quick googling reveals to me that most of the Feng Shui practitioners ignore making any changes at all AND it seems to work appropriately - as it is too difficult to apply all the changes necessary.

Things based on directions/coordinates would be switched/reversed. However many aspects have more than a simple direction in their 'definiton'

Ideally, for items located with the compass/pendulum - The Ba Gua {Hexagram baseplate} would be turned 180°, then read accordingly.

There would also be issues with the Zodiac Order if you did this.
And you'd have to re-prioritize some of the principles as they pertain to the Elements.
And basic issues of Chi and the Yin/Yang stay the same...

Can't imagine what one would do if you were on the North or South Poles...

Its actually reassuring that NO changes are necessary.