If you are willing to butcher smaller chickens, and just do more of them, you can skip that stage.We tried having dual purpose: white Plymouth Rock of a line that were good sized, meant for laying or for eating. Size was great, definitely attained a nice size by the 14-16 week mark. We kept 3 females for the flock and they are 16 months old and a very good size, and good layers. However, once they hit about 10-12 weeks, it was a bit tortuous to hear them crowing all the time, and bullying some away from feed (so extra management with that). Some got aggressive with us too.
But yes, I agree with the points you make in favor of Cornish Cross, and I agree it is worth considering other breeds if any specific one is not a good fit for the particular person raising them (speed of growth, amount of meat, stage of maturity, etc.)