you're still not gettin it. we haven't seen the extent of the cloaked form? why, it's pretty obvious if you read the manga. the cloaked form enables naruto to utilize 9tails chakra without losing control. the merged form does not. i told you before.
cloak: 9tails chakra without naruto losing control
merged: 9tails chakra with naruto losing control.
therefore, naruto can utilize the same power and chakra that the merged form possesses without losing control. get it?
as things stand now, why bring out the 9tails who would openly refuse to cooperate with naruto, when he can already use 9tails chakra with full control? that's the whole purpose of training with bee and perfecting cloaked form?
until naruto and 9tails can get along as well as bee and 8tails do, this 'merged' form you're talkin about is a no.