The problem with that is that you're always driving with a period of uneven treads. And you have to make twice as many visits to the tyre shop.
It's easier to just buy 4 every time and chuck the half worn ones away.
You're only rotating tyres so that you can reminisce on your death bed how you saved £1000 on rubber over your lifetime ?
Uneven treads? If we were talking cross axle sure, but front to rear? Not a problem.
And you don't do twice the number of trips, you extend time between trips as you replace all four when they're all worn.
