XF 2.2 Question: Extending $request->filter for existing filters?

[Zambfd]

I have written an addon through which our users can withdraw their quickpoll votes.

Problem is that for this I had to completely override the function "getPollInput" (XF\Helper\Poll) by the addon to add a new field called "remove_vote", because I have not found a way how to add a new field into the existing filters. This is of course impractical when Xenforo changes something here itself. Is there a more elegant way to simply add a new field to the existing poll filters?

Original \XF\Helper\Poll.php

public function getPollInput(\XF\Http\Request $request)
{
   $input = $request->filter([
      'poll' => [
         'question' => 'str',

         'existing_responses' => 'array-str',
         'new_responses' => 'array-str',

         'max_votes_type' => 'str',
         'max_votes_value' => 'uint',

         'close' => 'bool',
         'remove_close' => 'bool',
         'close_length' => 'uint',
         'close_units' => 'str',

         'change_vote' => 'bool',
         'public_votes' => 'bool',
         'view_results_unvoted' => 'bool'
      ],
   ]);

   return $input['poll'];
}

New \Our_Addon\XF\Helper\Poll.php

public function getPollInput(Request $request) {

   $input = $request->filter([
      'poll' => [
         'question' => 'str',

         'existing_responses' => 'array-str',
         'new_responses'      => 'array-str',

         'max_votes_type'  => 'str',
         'max_votes_value' => 'uint',

         'close'        => 'bool',
         'remove_close' => 'bool',
         'close_length' => 'uint',
         'close_units'  => 'str',

         'change_vote'          => 'bool',
         'public_votes'         => 'bool',
         'remove_vote'          => 'bool',
         'view_results_unvoted' => 'bool'
      ],
   ]);

   return $input['poll'];
}