Hi AP,
The FI AR DS does not support Direct access so you cannot use any standard cubes/DSO to reconcile.
What we have done is creating a alert report whenever the data mismatch is seen after the data load.
You can achieve this by creating a view based extractors on BSID and BSAD with direct access and push data to BW (creating Virtual Cubes). Then you can create a new MP based on the virtual cubes and the standard DSO 0FIAR_O03 and do a bex out of it.
We have done this to reconcile the data we are loading every day vs data posted in ECC.
The same can be followed for FI - AP.
Hope this helps...