It's difficult to say Tomek. As you know, tags are intended as a way of categorising and grouping items, and not as item data storage. In earlier versions of BP you could not update the queue item collection, so users turned to tags as a way to preserve runtime information. We made a mistake in not foreseeing this, and the consequence was that some users created hundreds of thousands of unique tags, which had a detrimental effect on system performance. My feeling is your idea would be OK provided the volumes are not to crazy. Changing the tag for another deletes the item-tag reference, but not the tag itself, it becomes an orphan in the BPATag table until it is automatically cleaned up. I can't remember how often the clean up occurs, but provided the build up of orphans does not get too great (as it used to years ago), then you should be OK.
