The difference between the Jag 4.0 and the Lincoln 3.9 is nothing more than cylinder liners. The LS has them and the Jag has none and uses, IIRC, a nikasil coating. The Jag needed the blower to compete with AMG and the "M" cars. If Lincoln had actually sold the LS worldwide a blown engine may have been in the works. Then again, why have one of your cars compete with another? Then, things started unraveling in ~2004 for the LS and the writing was on the wall.
You lamenters of the lack of an aftermarket need to realize to whom Lincoln marketed the LS. They were, right or wrong, after the BMW buyer. How many BMW owners modify their cars? For that matter, how many Jag or any other luxury brand owners modify their cars? The price of a used LS has fallen so much as to allow buyers who couldn't normally afford a luxury car to be able to purchase one. Lincoln never dreamed that an 18 year old would be able to afford the LS. Remember, these cars were near 50 large when new.
The LS never was and will never be (without taking away the luxury) a stoplight racer. It is an exceptionally well handling and reasonably powerful car when new.