Raise an alert with specific resolution state

Hello, 

I want to clasify the alert  by priority in a dashboard.

Priority field only manage 3 states, informational, warning and critical and I need extra states.

I think that the best way to achieve it is using resolution state to filter by this field, but I need to set automaticly the resolution state value when the alert is raised, not manually.

Any other idea to clasify or do a view with fields.

I was thinking in Coustom fields in alerts rules as well, but AFIK it can´t be overwrite on sealed management packs, just priority and severity fields can be overwrite

Thanks.