Hi Pankaj,
Interesting question, but I am not completely clear on what you are planning to do,
Also are you going for Sfin 1503 on premise/ Sfin 2.0 or are you using Sfin 1.0
From the post I think there are two route you may be talking about:-
Option 1- Migrate all Company to EHP7 and then upgrade to Sfin 2.0
If you are using Simple Finance 2.0 then the balances are moved as part of the migration steps.
So technically your company codes should be in the SAP system and then you can upgrade / install Simple Finance.
Option 2- Migrate to Sfin 2.0 and then upload the company codes from Non SAP
I think you are looking for option where you upload the balance for the company code once you are already in Simple Finance system. All the modes you have mentioned- Bapi, Idoc and LSMW, all works and there are not major technical change on Master data creation side.
But in this approach there are a lot of possibility of errors ( my guess
)
Also check blog by Arnaud Migration to Simple Finance
Hope this helps,
Regards
Rishab