It would indeed be good to have tags for all authors that have a significant number of questions on the site.
Whether "significant number" means one or ten is a matter of taste, but I am certainly not opposed to adding author tags to more questions and creating the tags as needed.
On a beta site like ours, anyone with 150 reputation can create tags.
Some SE sites frown upon creating new tags without prior meta consultation, but I see no issue for our site.
If you have specific tag suggestion, you can always ask others to create the tag for you.
You can post a request on meta, leave a comment under the question, ask in our chat, or flag the question for moderator attention.
We have so few flags that there is no risk of flooding the flag queue.
Once a tag is created, you can go and add it to other questions.
If you are below 1000 reputation, your tag edits will be reviewed before coming into effect, but you also earn reputation with approved edits.
I prefer to keep the tags concise, so I would rather have cicero than marcus-tullius-cicero or author-cicero.
However, tags can have alternate names.
It is possible to create a tag author-cicero and merge it with cicero so that the tag cicero shows up when one types "author" into the tag search tool.
Your point about searching is a good one, but I'm not sure if it's useful to be able to search for all author tags at the same time as opposed to searching for a single author at a time.
Such alternate names cause little or no harm, so if others agree, it's fairly easy to implement.
An alternative solution is to have a meta question for listing all author tags so that they can be found in one place.
The best choice depends on what you and others would like to achieve with the ability to do such searches.