Lucid VP Zak Edson told me that the Air platform was designed to take up to four motors, so I don't think there was much in the way of chassis modification for the tri-motor car. Edson added, however, that there were no plans actually to put four motors in the Air but instead to reserve that configuration for a future truck built on the same chassis. Or maybe a performance version of the Gravity SUV . . . ?
From early days, Peter Rawlinson has said the Lucid business plan was to get a foothold in the market by building brand reputation via products at the high end of the market, as those models would provide the margin needed to get the company through its initial financial stresses. With the resulting brand recognition it would then be easier to meet the much larger capital demands of mass production of lower-margin (i. e., less expensive) cars.
I think right now Lucid is still in the brand-building stage, especially as fewer Lucids have made it onto the highways thus far than was hoped. And a product such as the Sapphire, which dusts the best Tesla has brought to bear after 10 years in the market, is just the ticket to take the brand recognition to the next level. While most of the customers for more economical cars cannot afford a Sapphire, many of them will be proud to have their cars bear the same brand name as the mighty Sapphire.
Many buyers aspire to the totally underwhelming Mercedes GLA, not because the car itself is anything special, but because their car will have the same 3-pointed star on it as an S-Class or AMG variant.