Hi,
instead of reclassifying during the load process we often use a script and a separate datasource. So we load to the original account and then on a separate datasource we move the data from the original account to the new technical account. Neither of those two datasources would be open for journals and we will perform a carry forward of opening balances on both. So far this has worked quite well for us even on accounts where we load/use flows instead of just a balance.
BR,
Arnold