1) It would be redundant as Story could repeat.
: It could not repeat as Obito was only Juubi Jin to give us taste of it's power... remember that he was holding back avoiding massive killing but Madara doesn't not care and only wish to put humankind into sleep. It could also gives great challenge to Naruto and Sasuke and push them to their limits...
2) What was the point of Obito being Ten tails host then ?
- give us taste of ten tails power
- shows to us the weakness of Ten tails host:
3) Ten tails was shown as disappointing beast, so what could be the point to ressurect it once again
- Ten tails was not complete and didn't show all of it's power
- Obito was holding back just caring for everyone to give up and accept his plan while he realize it.
4) What could Madara as Ten tails Host bring fresh to the manga ?
- Possesing Senjutsu so he could have truelly no weakness
- Awesome battle
- See full potential of Edo Hokages... especially Hashirama with his Buddha Statue
- gives Naruto and Sasuke great challenge
- Not holding back and shows to use full power of Ten tails
- Possibility of getting more powerfull Ten tails beast then Obito had... as he can add complete Hachibi from Killer bee and some amount of Kyuubi cause Naruto has plot shield and can not be killed.
5) What would be the point of releasing Tailed beasts to seal them again
- Alliance Shinobi could interract and get more sympathy while also noticing they are not hostile
- Tailed beasts could thanks shinobi alliance by fighting and aiding them for some moment increasing strength of bond between beasts and humans.
- Naruto could talk with them and maybe get some present
- Naruto could get Shukaku and Gyuuki chakra so he could get complete of Tailed beasts chakra, maybe SOSP could appear inside him
- Tailed beasts could be shown fighting with their full abilities
- Irony of vitory earned by hard word to be lost in seconds in easy way... Kishi loves to troll.