Hi Kumar,
I think you will have to have downtime in case of direct delta update as you will not be able to import the datasource even if you have atleast one record in delta queue. Also I am assuming that you will also need to reload all historical data for your enhancement of datasource so better schedule a downtime. You can refer note 602260 - Procedure for reconstructing data for BW for things to be taken care for reconstructing the data.
If you don't need historical data I think you should still schedule a downtime of atleast 30 min for import of new enhancements for datasource.
Alternatively you can change the update method for app 11 in LBWE for some time and then revert it back when your changes are moved into Prod.
Also don't forget to clear detup tables before import.
Thanks
Amit