The current foot sensor is not connected to the frunk controller at all. Behind the tow hook cover are two cables - one marked negative, one marked positive. The frunk controller connects to the positive wire. When the frunk sensor has been triggered it applies voltage to that input - which connects with VCFront. VCFront is programmed to pop the trunk when it gets a signal on this wire if a) 12V battery is dead, OR b) car is unlocked.
The signal wire from the frunk controller could probably be hooked to the front controller if it has a free input. The frunk controller has a CAN bus connector, but a lot of owners are understandably hesitant to connect 3rd party devices to the CAN bus. There is most likely a signal on the CAN bus that be intercepted, but it might be a huge effort. The security module might send a "authenticated_user_nearby" signal, which the frunk controller could monitor. Or, it might be setup where when the door sensor is tripped, vcright or vcleft interrogates the security module asking "Is there an authenticated user nearby?" Then the front controller would have to ask that question itself. Depending on the amount of security in the system it might be tricky. And might break from update to update.
I think we're better off finding out where the Tesla programmers go to drink, buy them a couple, and bring up the idea that VCFront should allow the emergency external frunk release when an authenticated phone is nearby instead of waiting for the full unlock sequence.....
Or live with it how it is. It's kinda like how you have to nudge the door handle before you can take the charge cord out in the morning. On the way to the frunk just hit the door handle and let it open slightly.