Strange article. Even the proposed "50% degraded" MS85 has 132 miles EPA vs a gen 1 Leaf at 73 or a brand new gen 2 84 miles. Unless you could get that 85kwh pack down to maybe £5k then it wouldn't be worth putting it into a car that age/mileage. I believe Tesla are shooting for something like a 25% reduction on a current cost of about $30k.
That is for a moment assuming 50% loss actually happens. That seems unlikely without thousands and thousands of cycles. Bear in mind that 1,000 cycles in a Leaf is 73,000 miles and in an S85 it's 265,000 using EPA range. We're seeing 15% loss in a Leaf at ~650 cycles. For the S85 that's 172k miles, but let's not forget the Tesla pack is thermally managed and running at much lower C rates during both charge and discharge.
The article seems quite uninformed to me