Giving up the info on the key seems silly to me.

You may not have to have your key in your hands, but you will still have to have your fob on you. Unless you get an RFID implant in your hand. That would be cool. Freaky, but cool.

Yes, the service department may have issues working on your vehicle. Worst case is you would have to remove the mods to diagnose an electrical problem. Your aftermarket system will be suspect for any electrical malfunction, quite properly.

Seems you would give up the built in immobilizer, and rely more on a perimeter defence. May or may not impact your insurance rates.

General wisdom in doing it? Many/most problems with modern BMWs are electrical, IMO. Why do anything that makes that situation worse?

I have had comfort access (OE) on a few vehicles. Works fine. But so did pressing the unlock button on the fob. You still need a hand free to work the door handle, so I don't see a big advantage.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue