Hi Venkat,
Thanks for your response on this query.
Most of your answers are applicable and can be done in the system.
However in your answers, the additional actions to reclass the journal from the sub group into the core group needs to be done by the sub group, while this reclassification does not really affect their reporting. The reclass in my case should be done by the core group, because they require these journals for their own reporting. If we want to make the reclassification to be done by the sub group as in your answers, that means we need to give the write access to the data in the core group to the performer in the sub group. This access will give the performer of sub group to read and change the data in the core group, which should not be allowed.
Currently I have created a custom BADI to be executed by the performer of core group, to collect all the data posted by manual journals (filtered by specific audittrail) in all of its sub group, and write the data with the core group Group dimension members. This require extra efforts in ABAP and the creation of process chain and should be considered as major enhancement in the system though.
If you have any other suggestions, you are welcomed to give. 
Thanks,
Siswono