Unfortunately, Chan_SIP is deprecated, in extended support and is community driven. In order for this to be even close to being considered it will need to be submitted like any other patch and doing that in the issue tracker isn’t the right place.
At this time Chan_SIP is in the final countdown to where it can be removed from Asterisk (two years left). If you’re really going to add TEL support do it for Chan_PJSIP as that is the active and supported SIP driver in Asterisk.