The cloning is a copy operation basically, so it will depend on your SAN performance as well as the size of the VMDKs of the source VM (template).
You should also review if your storage device is using VAAI, which can have an impact on cloning performance.
Check if your VMDKs are thin provisioned, thick can take longer. You could look at using linked-clones if it is appropriate to your use case. If you are just using the disk to store some installation contents, you may want to look into a network storage solution (such as NFS, HTTP, FTP, CIFS). You could also mount the disk as you mentioned, assuming you had a common file system and took precautions for multi-consumer use of the disk (read only, shared mode, etc)