The rennegan that nagato have was transplanted, so there for rhe rennegan eyes would stay in the rennegan status, the same when kakashi took obito eye, the eye stayed in sharingan form.
So that bein said for someone to have renegan with full powers ,they must first pass through all the sharingan stages.to acquire the.maturity of their own eyes so their powers would advance ms -ems-renegan.
So its basedon an uchihas personal eyes an also expierencing the evolution change within his own eye power ,so that is howb madara can use ems power an also rennegan power. Because that is his eyes. He can use all the full powers of it from its first three tome state to ems an finally its rennegan state.!!!!!!!!!!!!