I would not recommend it. first there is the development issue's, if you breeding for the strongest genetic and doing so with the survival of the fittest technique then i would try it.(not a breeder but makes sense to me) Otherwise each different plant is going to have it own individual and unique set of needs both with nutrition and with light. Most of the autos i have seen flower early but there is still a great deal of variance between the start of the flower times. In addition to this the lenght of flowering time and nutritional needs based on flowering progress can seperate in a huge hurry. I have to add that this can happen even with 2 plants of the same strain, while they will alway be similiar there will always be some differences (assuming the best). And if your not into LST or some other training method forget it. This is what i learned from my current grow, while i am sure that there is some success with this method i would keep them seperate to better care for there individual needs. Not an expert by any stretch just my 
