Maintaining large numbers of client tnsnames.ora files is a pain. Oracle Internet Directory is the recommended solution to this, but it is not an easy exercise to set up or migrate to.
An easier alternative is to set TNS_ADMIN in all client PCs to use a single common tnsnames.ora file
All the client PCs need read access to that file, but don’t need write access.
One drawback of doing that is that if the network share is unavailable for any reason then all client connections will fail, so a highly resilient network share would be needed. A safer alternative is to set TNS_ADMIN to the same local disk folder on each PC
and rely on automated PC management tools like Microsoft System Centre to deploy the master tnsnames file out to each client PC at regular intervals.