If your really that worried then you can setup some external jump points, basically just run a feed from the live side of your battery down to somewhere where you can reach it from under the car, or into the inner wing, something like that, so you can still attach jump leads and get enough power to get in, whilst your going that far, might be worth storing a spare battery for your key fob
Not worth the hassle on a MK1 as they are easy enough to break into anyway!
Or just make sure you have a spare rear qtr glass sat at home and you can go all out and have fun bricking your own window lmao