It would be nice to have a radio button selection for Add or Replace tags in the bulk association wizard. Today the bulk wizard replaces any tags on the monitors that may exist with the ones added from the bulk association wizard. This means that monitors with disparate tags cannot be updated via the wizard. For example, if I have two monitors where one has a tag called "Production" and the other has a tag called "Development" and I use the bulk wizard to try and add a tag called "Windows Servers" to both of these monitors the end result is that the other tags are removed and just "Windows Servers" will be present. This requires a two step process to add both the "Production" and "Windows Servers" tags in one batch and the "Development" and "Windows Servers" tags in another batch to prevent overwriting the existing tags. The other option is to manually add the tags which defaults to adding the new tag without removing the old ones. This could be cumbersome for multiple tags.
If a selection was available to "Add" additional tags without changing existing tags this could be done in one process. To have the option to "Replace" the tags would be nice when this is appropriate.
To get really advanced you could either have separate add and remove boxes or have a check box next to each tag you are modifying to allow for an Add or Remove process. This would allow you to affect all of the monitors in the bulk process by removing the selected tag if it's present on the monitor or adding the tag if it isn't present. Otherwise the action would be ignored.