Rosengart just filed legal docs in which he agrees with Jamie Spears on one point -- the conservatorship no longer serves a legitimate purpose and should end immediately. Furthermore, Rosengart agrees with Jamie that the conservatorship should be terminated without any further medical evaluation ... something Britney expressed to the judge back in June.

Rosengart says there have been changed circumstances that warrant the end of the conservatorship ... namely, the judge already allowed Britney to select her own lawyer ... the point being she has the "capacity and capability to identify, engage, and instruct counsel of her own choice."

In the docs, Rosengart quotes Jamie's document, "If Ms. Spears wants to terminate the conservatorship and believes that she can handle her own life, Mr. Spears believes that she should get that chance." In effect, Brit and her lawyer are saying, True That!

Britney is asking that a "termination plan" be formulated immediately so the conservatorship could wind down in its entirety.

Now, the hearing a week from today is to get Jamie out of the conservatorship immediately, and Rosengart offered a litany of reasons why that must happen. He claims Jamie has raked in millions and he needs to be out immediately.

Rosengart says Jamie never had any business being a conservator ... he has no training in economics or finance and his own finances were in disarray.

Britney's lawyer says the judge should appoint a conservator of her estate on a temporary basis to replace Jamie while a plan is put in place to end the conservatorship altogether.

And, Rosengart confirms TMZ's story earlier this month ... that a family law attorney is already drafting a prenup between Britney and Sam, and the conservatorship of the estate may be needed to validate it.