Please refer to the attached before-after diagram.
The before diagram is the ceiling, as viewed from below. Dashed lines represent joists, not visible, but assume they can be located with precision using a stud finder. There is a pre-existing conventional light in the center of the ceiling; it will remain. Four "old construction" remodeling cans are to be added, from below, per usual. The ceiling is NOT accessible from above.
Refer to the after picture, which shows that four installed cans are to be powered from the pre-existing light in the center of the ceiling.
The obvious challenge, given the insulation and joists, is to somehow "fish" the new Romex past all the obstacles, but in the most efficient way. Is the only recourse to either remove or RotoZip the wallboard? Are there any tricks or tools by which to minimize the work involved in this project?