I'd be concerned about individual contractors ghosting before or mid-project, throwing the whole plan into jeopardy. I doubt many contractors would be willing to continue someone else's work. Also, storing the materials can be a hassle -- the panels alone would take up half of my garage, for an unknowable amount of time (it takes months to find contractors willing to bid on projects around here).

At least having an experienced general contractor overseeing the project reduces the chance that an individuals' ghosting could cause large delays.