Is it wise to create indexes for the replication server only?
This is a common requirement.  Transactional Replication is typically used to off-load reporting to another server/instance, which can be near real-time in a best case scenario. One of the benefits of Transactional Replication is you can place different indexes on the subscriber(s) to optimize reporting.  Another benefit is that you can choose to replicate only a portion of the data if only a subset is needed for reporting.

So to answer both of your questions:


You are taking the correct approach.
This is a common requirement and is not a bad idea at all.


Just keep in mind that the indexes that you place on the subscriber(s) will need to scripted out and included in a post-snapshot script in case you ever reinitialize the subscriber(s).