What would happen if the phospholipids in the phospholipid bi-layer were reversed, the fatty acid tails now facing outwards and the phosphate heads facing inwards? I'm assuming this will not affect the protein channels, but perhaps the loss of cholesterol in the structure of the bi-layer. Would this then mean that the fluid mosaic model no longer holds?
This would have quite dramatic consequences. The layers are ordered in the way they are, because of their polarity. In the way they are ordered, the hydrophobic tails are inside and directed towards each other, the hydrophilic heads are orientated to the outside and inside. Since both sides of the membrane are surrounded by aqueous solutions, this is necessary to allow a contact between solution and cell membrane and to allow an exchange of molecules between them. If the layers would be oriented the other way, this contact and exchange wouldn't be possible. Proteins channels in the membrane wouldn't be possible as well, since the intermembrane domains are composed preferrably of amino acids with hydrophobic sidechains, while the domains on the outside of the membrane contain more hydrophilic amino acids. A turn like this would need a completely different composition of life - meaning it couldn't be based on water like it is.
Someone has thought this was a very good question and performed an MD simulation on spontaneous bilayer assembly. There, lipids start in random orientations. The ordered bilayers we know and love spontaneously assemble in under 100ns.
So if the lipids were jumbled up (or even reversed), the would probably reform fairly quickly. I wouldn't imagine that it would do the cell much good though...