Modifying Schema on secondary replica
Due to the "availability-groups" tag and the other terms you have used, I am assuming you are referring to a database in an availability group.

In short, the answer is no, you cannot do this.  The secondary database is read-only since it is a replica of the database on the primary.  If you removed the target replica from the AG, made the modification, and then tried to add it back to the AG, replication from the primary would no longer work.  The solution you are suggesting is 110% not possible with availability groups.

Since you can't modify the schema of the secondary replica, you'll have to start with a completely separate database for the reporting and keep it in sync with replication or an ETL process.  A lot more information would be required for anyone to be able to determine what would be the best solution.