Hi Raznan,
TRM will require Business partners (BP roles: counterparty for OTC products) and financial instritution that you conclude deal with must be set up as BP Counterparty. Indeed, BP could be syncronised /integrated with Customers and that TRM would be able to post the deal to create finacial documents into customer subledgers, instead of GL postng/payment requests.
I have come across a few reason that some companies needed to integrate BU Finacier as customers, such as applying WHT receivalble function on interest, necesity to generate an invoices, having the different date between due date and payment date for the interests incurred.
I am not sure you can integrate BP to GL account, let alone , from TRM point of view, that is not relevant. If I were you, i would maintain them off line for now and define BP only or if necessary also as customers.
Hope that this helps.
Cheers
taro