Namespaces and modules are orthogonal, you can support both like Typescript.

Your solution works, but unfortunately not something that has any community support. I proposed something similar a year ago but use classes instead because classes seems to be the internal building block in PHP.

For both our solutions is would relatively easy to add a shim to older PHP versions.

module.php

    <?php
    
    return new class {
        public const MY_CONST = 47;

        private const MY_PRIVATE_CONST = 127;
    
        // with PHP 8.1 you also have readonly properties
        public string $myPublic = 'foo';
    
        private int $myPrivate = 17;
    
        public function helloWorld(string $name): void
        {
            echo "Hello, World {$name}!";
        }
    };

main.php

    <?php
    
    final class ModuleException extends Exception {
    }
    
    function module(string $name): object
    {
        static $modules = [];
    
        if (isset($modules[$name])) {
            return $modules[$name];
        }
    
        try {
            $module = @require $name;
        } catch (Error $error) {
            throw new ModuleException("No such module {$name}", 0, $error);
        }
    
        if (!is_object($module)) {
            throw new ModuleException("Module {$name} is not an object");
        }
    
        $modules[$name] = $module;
        return $module;
    }
    
    $my = module('module.php');
    $my->helloWorld('Module system');
    
    $other = module('module.php');
    assert($my === $other);
    

https://news.ycombinator.com/item?id=30242974