Thank you for this thread as it was of great help in getting my LCD with ILI9341 working with 16bit. Just a follow up for others that may have the same problem:
Can confirm that the procedure that David posted for modifying UTFT works using the ILI9327/initlcd.h and ILI9327/setxy.h files. That is, when creating the new controller (eg. ILI9341_16), copy the ILI9327 setxy.h and initlcd.h files for the driver.
If you are in a hurry/lazy you could also simply change the dsy[] entry for ILI9327 in "UTFT.cpp" to match the 240x320 display of the ILI9341 (the ILI9327 is 240x400 16 bit) and then use the ILI9327 controller in UTFT.