Madara's planning is as best as he could do. Times can change and after he is dead he can't change what other people do. So yes while he is dead his plan is based on luck, but he can predict a high chance of it succeeding.
Obito falling into his lap? Maybe not part of his plan, but it was his plan for someone to carry on after he was dead so he would get one eventually before dying and while he was connected to the gedo he wasn't going to die.
He left the convincing of Nagato up to Obito, and honestly regardless of whether or not Nagato betrayed Obito there was nothing Nagato could ever possibly do to even harm Obito, so Obito could have forced Madara's revival and Madara knew that. Madara also knew that if Nagato died Obito could take the rinnegan and revive him. He also planned for it to be possible for black zetsu to be able to control another person and force them to revive him. Madara also knew that edo tensei exists and if someone wanted someone powerful, he would be a person to go after. So no matter what Madara thought there was a high chance of his revival, you can't force something to happen when your dead but he can plan it very well. Which he did.
Even if Obito had a hole in his chest and was lowish on chakra, he still wasn't really near being dead. You forget nearly half of his body was crushed before and he survived. And nearly half of his body is constructed of extremely strong zetsu goo which pretty much forces him to live. Plus Obito has a huge drive from Rin to overcome Madara's control. A normal person definitely wouldn't have been able to resist control. Eventually Obito succumbed when he was truly in a weakened state, Which Madara was planning on doing himself, but instead got to have fun fighting Hashi.
The armor thing you bring up is pointless. He probably would have taken it off anyways since he wanted to feel the fight, and honestly needs to feel the fight since he is blind. He can't feel wind created by movement as easily with a bunch of armor on, it also might slow him down. Also he probably wanted to show Hashi the face on his chest and explain to him what was up, so taking off the armor was likely part of his plan. Sasuke's amaterasu had nothing to do with it.
You are right he tries to fight the strongest entities in Naruto and fails at first, but remember he is doing this with no eyes and still managed to survive. And after obtaining one eye he subsequently knocked all those entities down by looking at them and then forcefully made them his *****es.
Madara's plans take their own shape after he is dead and he doesn't have direct control over them, but he set up his plans very well and knew his plan of being revived would most likely come to fruition. While he is edo and brought back to life he makes his plans happen while having fun fighting. IMO he is great at planning. How many people could honestly prepare a long term plan like Madara's and actually have it work? Maybe only someone with the ability to see the future.
