All BMW RFTs seem to suffer from inner edge wear, but that's pretty bad!
First thing - tyre pressure. Are you running what is recommended on the placard in the drivers door?
Second - as above, have you had a 4-wheel alignment recently? If not, get one done.
As for switching to non-RFT, you won't regret it if you do!
It's a pretty absolute no-no to mix RFT and non-RFT, so if you want to do it, you'll have to replace all 4. You can offset the cost by selling the part worn RFTs on here on eBay - there's a surprising market for them.
Just how many Yorkshire sheep can you fit inside one exhaust?