Transaction Integration -> Lawson A/R

We are required to integration transactions (Invoices, Debit/credit memos) from a non-Lawson billing application -> A/R. The billing application will be an in-house J2EE application - so ideally, we would like to enact this integration on a real/near-time service basis.

Existing transactional integration to A/R is kind defined as a 2-step, batch-oriented approach:
1) Populate ARITRANS/ARIDISTRIB and optionally ARIITEM - via AR97.1,AR97.2, AR97.5
2) Execute batch job of AR560 to move data from staging tables to actual tables

The on-line method of introducing transactions is also multi-step/clunky: Batch header, details, batch release, etc.
We are quite familiar with leveraging the API's - and for data integrity purposes, this would be the way to go - but since they are based on the form definitions -seemingly locks you into this multi-step approach.

Am I missing something??  Can someone suggest an approach that I have possibly not conceived of?  Appreciate everyone's time here.