m2e automatic invoice upload and xtento

I want to turn on automatic invoice uploading on amazon . I am using m2e pro extension and it has that option but it still uploads basic magento invoice instead of my custom one which is created with Xtento pdf customiser.
M2E pro SendInvoice is using MagentoSalesModelOrderPdfInvoice

pdf = $this->pdfInvoice->getPdf([$invoice]);
$documentNumber = $invoice->getIncrementId();
$documentPdf = $pdf->render();

I am thinking about creating a plugin or overriding that function to let it generate pdf through xtento instead of magento sales model .
I think in general if your default pdf is xtento one it should automatically generate that type of pdfs. but couldn’t find option for switching etc.
any good ideas?