2. If you want to show profit center inside a deal/transaction - use custom tab Custom Screen in Transaction Manager, Facility
And if you want to make posting with Profit center from your deal/transaction, but without configuration in SM30 -> TRACV_ADDACCDATA - use badi TPM_ACCIF_TRAC, method ACCIT_EXIT
It is a task for your ABAPers.
1. Aks them to append Profit center field to VTBFHA.
2. They have to implement FTR_CUSTOMER_EXTENT using this article Custom Screen in Transaction Manager, Facility
3. They have to draw Profit center field connected to VTBFHA-your_profitcetner_field. So users witll have Profit center field inside transaction on customer tab. and they can enter needed profit center.
4. Implement badi TPM_ACCIF_TRAC, method ACCIT_EXIT - it has to get profit center from screen (3) and put it in one of the ACCIT structures from ACCIT_EXIT structure. Remeber that Profit center is CO object, so it has to be posted with P&L account.
That's all.
I hope that idea is clear. If not - ask questions.