The search engine is made using Google's API, so it would only search for posts. This could be made possible with a simple if statemnt in JavaScript. Here is a PoC:
if(userExists){
//Redirect to user's page
}else{
//perform google API search
}
I can surely implement this feature. Is the code for steemit public? If it is, I can submit a Pull Request.
RE: Suggestions for the search menu in steemit, when typed in the user name if it corresponds directly to the profile