Not sure if this would be possible at all but surely going to be expensive if not prewired. Tow bar for example can be retrofitted by Porsche for around 2k as it is prewired. Best to ask your dealer.
As far as I understand, the ACC needs additional sensors that cannot be installed and calibrated at a service center, it has to be done at the factory. My guess is you're better off selling your current car and buying one with the feature you want instead.
I agree that ACC can’t be retrofitted (easily and economically) on the Macan EV due to the extra hardware that’s required, but if the sensor calibration can’t be done by a Porsche Service Center then we’re completely screwed if the car is involved in a collision. The PSCs must have the ability to perform the calibration.
I doubt it can be retrofitted. and it would be a stack of cash. A range of sensors needed, including a camera and module that sits in front of the r/v mirror. As an idea, the camera module in my old Audi A6 went - the replacement module could only be calibrated by Audi - about 4 hours labour for that bit alone. All in it would have been around AU$4000 (I found someone who could refurbish the existing module and did the labor myself, so didn't need to use the stealership).
And that's just the price for one circuit board + calibration....
I know Porsche is "separate", but they're part of VAG, so they may tow the party line of not upgrading to try to force you to buy again. As an example, my M/Y Audi had all the hardware to support Apple carplay/Android Auto, but Audi refused to enable it despite it being a pretty simple software hack. I did it myself in the end, but it was a tense few hours of watching the MMI and hoping that it wasn't busily bricking itself.
ACC uses the RADAR located in the front grill below the license plate.. It does not use the less reliable optics approach like many other cars.
The RADAR is also used for the optional forward collision warning/avoidance (PAS) feature. It may also use optics to reduce false alarms. Standard forward collition warning uses cameras.
Because the RADAR unit is used by two or more features, there would likely be some integration hassles.
Last I checked, a comparable RADAR was in the $3000 range.