Hi Bharat,
I don't believe this is the right approach.
Usually, for migration purpose FI team prepares special GL account for the postings from conversion trade FICA documents.
However, if you do not have any special GL accounts for this purpose, I think the better way of doing it is to post an offsetting FICA document during the time you post the conversion documents.
The offsetting FICA document will not have any entry in DFKKOP. Simply, it will have entry in DFKKKO (a header record) and DFKKOPK (with GL level posting details).
You can achieve that easily by enhancing in fqevents (0030) such that the enhancement would identify the posting of conversion document and post another FICA document along with that.
So, if you transfer reconcilation key for both the FICA documents, it would not impact the overall balance of GL accounts.
Hope it helps.
Regards,
Bodhisattwa