Is it even possible to do something like this in codeigniter?Is it considered a good practice in general?
Yes it is possible.
I do it all of the time, if the data is not from post I can send it to the model.
$this->load->model('some_model');
$this->some_model->some_function($var);
What data do you want to send to the model? This will help in deciding whether it is bad practice.