If it is just a story without pictures loli or not loli depends on their behavior and emotions not on breast size desire to look more grown up is loli behavior.

But speaking about your story idea, I do not understand how becoming a meat will make someone more grown up or make their breast bigger. Do you suggest some stuffing?
If that's the case, Yes, I woud love to see this story.

But I generally do not like reusing characters from other fiction in "out of character" way. So Lucky Star is not a good choice because none of those characters could even be imagined doing such thing.
Better just create original characters or if you reuse existing ones treat them like they are original.