Does anyone remember that in "here comes tomorrow" evil subline/beast hatch the "phoenix egg" using like 20 nightcrawler dubbed "crawlers" clones who had cyclops eye blast. Then in endsong and warsong the phoenix could still obsorb cyclops eye blast. Then in AvX they totally dropped that. Whatis up with that?????

different writers not respecting the story aspects that have already been set in stone by their preceding writers

The Phoenix can absorb all kinds of energy from a star to life force. Using heatless optic blasts to incubate an egg was stupid. The using of Scott in endsong had more to do with the Phoenix being confused, she could have just as easily ate the sun, but in her confusion feeling Jeans desire to feel and live she went after Scott. Since the Phoenix had memories from HCT in Endsong one could speculate that she remembered being incubated by the crawlers and that is what led her to believe his optic blast was an adequate energy source.

thats part of the main thing with the phoenix. the force itself since first taking jean's essence is dependent on Jean to be whole. the phoenix force and jean grey are bonded forever. thats why the force returned for her once it was injured. only with jean could it find its missing pieces. i dont necessarily think the force really needed scott's optic beams to feed of more so like you said the blending of its own conscience and jean's made it take two different things and merge them together. the phoenix force in jean's form would hold the power of scott's blasts at bay allowing him to share his full self with her same as was attempted in the begining of the story with scott and emma but him telling emma that it wasnt the same. that whole issue in endsong had mainly to do with dependency. as far as the crawlers in her comes tomorrow.... maybe the same thing could be said with the optic blasts. it was about familiarity more than anything.. the familiar sensation of the optic blasts prompted the phoenix egg to open because it knew the power that was bombarding it