When you buy-out the lease, you’ll receive the released title from MFS. At that point you have to retitle the car and pay the sales tax anyway, you could (for example) title it into your spouse/partner’s name at that point when you are surrendering your license for a non-driver ID. Then you wouldn’t need to be on the insurance.
If you want to buy it and sell it to a family member, CA allows you to recover the sales tax in 10 days. You will need to retitle to yourself first, pay the tax and then “sell” to the family member and apply to recover the tax.