MyMiddleware.php

<?php 
namespace Acme;

use Symfony\Component\HttpKernel\HTTPKernelInterface;
use Psr\Http\Message\RequestInterface;

class MyMiddleware implements HTTPKernelInterface {
  
  private $kernel;
  
  public function __construct(HTTPKernelInterface $kernel)
  {
    $this->kernel = $kernel;
  }
  
  public function handle(RequestInterface $request, $type = self::MASTER_REQUEST, $catch = true)
  {
    // One option
    $myRequest = new MyRequestDecorator($request);
    
    // Another Option
    $myRequest = MyMutableRequest::createFrom($request);
    $myRequest->setQueryParams(['foo' => 'bar']);
    
    return $this->kernel->handle(
      $myRequest,
      $type,
      $catch
    );
  }
}

MyMiddlewareConsumer.php

<?php
namespace Acme;

use Psr\Http\Message\RequestInterface;

class MyMiddlewareConsumer {
  
  public function doSomeRequestMagic(MyRequestDecorator $request)
  {
    // Here I expect a modified request
  }
  
  public function doMoreRequestMagic(MyMutableRequest $request)
  {
    // Here I can modify the request myself
  }
  
  public function doEvenMoreRequestMagic(WritableRequestInterface $request)
  {
    // Here I can modify the request myself, without coupling to (a|my) concrete implementation
  }
  
  public function doSomethingNotRelated(RequestInterface $request)
  {
    // Here I can't modify the request
  }
}

MyMutableRequest.php

<?php
namespace Acme;

use Psr\Http\Message\RequestInterface;

class MyMutableRequest implements RequestInterface {
  
  public static function createFrom(RequestInterface $request)
  {
    $myRequest = new static;
    $myRequest->setQueryParams($request->getQueryParams());
    $myRequest->setProtocolVersion('1.0');
    // ...
    
    return $myRequest;
  }
  
  public function setQueryParams(array $params)
  {
    $this->queryParams = $params;
  }
  
  // implement any other setters as needed, and missing methods...
}

MyRequestDecorator.php

<?php
namespace Acme;

use Psr\Http\Message\RequestInterface;

class MyRequestDecorator implements RequestInterface {
  private $request;
  
  public function __construct(RequestInterface $request)
  {
    $this->request = $request;
  }
  
  public function getQueryParams()
  {
    return ['foo' => 'bar'];
  }
  
  // Act as a proxy for all other methods...
}

WritableRequestInterface.php

<?php 
namespace Acme;

use Psr\Http\Message\RequestInterface;

interface WritableRequestInterface extends RequestInterface {
  
  // You could even decouple your own code with this one, without forcing it to others
  public function setQueryParams(array $params);
  
  // ...
}