There are several options on leasing. You can lease with the intent of turning it back in at the end of the lease. However, you can also lease it with the option to purchase it at the residual value of the lease.
This works quite well when you lease it through the business. It is easier to qualify a vehicle for deduction if it is leased. You can set up the lease with whatever mileage per year you want and then, at the end of the lease, buy it personally.This can have significant financial benefits.
If you do that, then you can modify it however you want. You just have to return it to its original when you turn it in, or buy it. I have bought all of the vehicles I have leased through the busines. Just treated them as my own during the lease because I was buying them anyway.