I know it’s not possible now – that’s why this is in the wish list! ?
But look, if you want customers to have a path forward for moving from SIP to PJSIP, while at the same time benefiting you as the provider/supplier so that you can ultimately move away from chan_sip entirely, then the time invested to create the process for conversion will be worth it for both parties.
I’m just sayin… There are robots on Mars. Of course it’s “possible” to program a conversion in VitalPBX.