How to include add_filter() in a condition based on $post data

Question

I'm writing a plugin that has a custom page for displaying user stats: example.com/user/admin/ has a custom permalink structure that takes the reader to the /user/ page and display the data for the 'admin' user. Meanwhile, example.com/user/ should just return a list of all registered users. What I have done (that works) is have a code something like this:

function user_heading_func($heading)
{
    $post_slug=$post->post_name;
    if( $post->post_name != "user" || !in_the_loop() ){
        // Do nothing
    } else if ($wp_query->query_vars["u"]) { // checks if user is defined in permalink
        $heading = "User data on ";
        $user = get_user_by("slug", $wp_query->query_vars["u"]);
        $heading .= "" . $user->data->user_login;
    } else {
        $heading = "User list";
    }
    return $heading;
}
add_filter('the_title', 'user_heading_func');

And then repeat an almost identical code for the other filters like the_content and document_title_parts.

What I want to know is how I can simplify this down a bit by having the filters in the condition rather than the condition in the filters. Something like this:

global $post;
global $wp_query;
if($post->post_name != "user"){ // Normal page
    // Do nothing
} else if ($wp_query->query_vars["u"]) { // User page with defined user
    $user = get_user_by("slug",$wp_query->query_vars["u"]);
    $heading = "User data on ".$user->data->user_login;
    $name = $user->data->user_login;
    add_filter('document_title_parts', function($title){ // Edit the <title> tag
        $title["title"] = "(user)'s profile";
        return $title;
    });
    add_filter('the_title', function($head){ // Edit the <h1> tag
        $head = "(user)'s profile";
        return $head;
    });
    add_filter('the_content', function($content){ // Edit the main body content
        $content = "(user)'s profile data content goes here";
        return $content;
    });

} else { // User page with no defined user
    // Similar to if ($wp_query->query_vars["u"]) but with different outputs
}

Answer 1

When using anonymous functions in filters you will be unable to remove them later:

Important: To remove a hook, the $function_to_remove and $priority arguments must match when the hook was added. This goes for both filters and actions. No warning will be given on removal failure.

Source.