Even though many of us probably would not care to eat such a combination I think it is possible.
The above link to using cheesecake as a wedding cake does not work for me :(
Cheesecake is going to be too soft for fondant icing. I suggest using a soft b'cream.
This probably is the time for you 'professional knowledge' come into play :) Try to explain to the bride this is a combination most people would not care for., then suggest that every other tier be cheesecake so guests can have their choice.
OR (I'm wondering) make a layer of each but instead of cheesecake on top of cake cut the layers in 1/2 & stack then shove one 1/2 round of cheesecake & one 1/2 round of cake together so each tier is actually 1/2 & 1/2 - UUUGGG this is hard to put into words - I hope you can picture what I'm trying to say.
Not sure how this will be covered in icing - that's why I suggest using a soft b'cream to make applying it easier.
Sure hope you have time to experiment with this.