Equivalent SQL Server's Backup COPY ONLY in DB2
As far as I know you can't do that with DB2. Deltas and Incrementals will be based off of the last full backup taken (either offline or online). If anything it would cause one to adjust your recovery strategy for that week.

If you needed the data however, why not just copy the backups you need (the full and any deltas/incrementals) and restore those elsewhere, rather than taking a full backup? Or use db2look and db2move to extract the data for test purposes?

Otherwise I know IBM does have a product called IBM DB2 Advanced Recovery Feature (it was formerly an Optim product if I remember right). It has a subcomponent called  IBM DB2 Merge Backup for Linux, UNIX and Windows that allows you to combine the full backup with subsequent deltas and incrementals to create a full backup to restore to. This gives you the advantage of only needing to restore one backup, rather than progressing through the deltas and incrementals.