Ummmm read the manga he told Nagato he would show him the true power of the rinnegan. Secondly I know you need both eyes but why wouldnt he just have Nagato revive Madara and Rin.plus he doesnt know any rinnegan techs
That makes sense. Plus Rin can always die again in the real world. Gee I really dont like this love for a girl being the fuel to obito's rage and ambition1. Even if Rin came back using the Rinne Tensei, its not like she is going to love a 30 year old man who has one side of his body crushed even if it is Obito
2. I believe Obito would prefer to have Rin revived in the 'dream world' because there he can make Rin love him by changing his appearance to look normal etc.