Huh? What prevents you from installing them "all at once"? The downside is obviously a long stretch of no sun, and for Europe winter being both low solar production and high energy demand due to heating which the soon-to-be-cheap grid scale batteries don’t really fix. The logistics of PV don’t seem difficult though - it seems by far the easiest of the power generation methods, even if the synchronization can get a bit tricky in a large grid.