>>“I’d like to find a way to then automatically close the deal itself (changing both the “deal stage” and “close lost reason”) as well as automatically close out the task.”
No built-in native HubSpot functionality to trigger deal closure (or state changes) from Sequences.
An alternative approach may be to delay deal creation until interest is established and opportunity exists. This (best practice) will eliminate the need to clean-up extra deals and give your conversion numbers greater meaning.
- se Manage lifecycle stages sync settings (Deals section)