...WHAT!

What fool would complain about that? Ridiculous engine swaps is on the list of things GT needs in the future. Who in their right mind wouldn't want the option of repowering their car and building wild one-off* virtual customs? Having such extensive modifications available to the player
combined with Gran Turismo's physics, gameplay, variety and attention to detail would probably dwarf all other racing games period. It would make for practical uses too, showing the theoretical results of a real-life build, for example.
Remember there's a looooong list of things for the series yet to implement, and most of them won't happen at least for a few years. You can be sure this one (ought to) be at the top of the list. Pardon the rant..
I want to cram a V12 into something small
*Presuming there are enough options to create something "one off", though considering the number of options and number of players playing the game, there will probably be no such thing.