ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
Also there is another OOTB index (index_party_key), this looks more similar to above index index_key_purp, when is this index used, will there be any impact if this index is deleted, having additional indexes might impact insert / updates.
/****** Object: Index [index_party_key] Script Date: 11/04/2016 10:49:53 AM ******/
CREATE NONCLUSTERED INDEX [index_party_key] ON [dbo].[pc_index_workparty]
It is not good idea to delete or modify the existing index in general. Because whatever is provided OOTB is developed for solving some purpose and if you delete/modify it will impact some functionality.
If needed you should go for creating new index I would suggest.