If you want to make major mods it makes little sense to lease. First of all your lease will be held by BMWNA so you will have to deal with them and will not get a great deal as used cars are hot right now.
It also makes no sense to mod a car if you think you will get sick of it in a few years. You are limiting the market by personalizing the car.
I lease because I like to get a new car every 3 years and don't drive a lot. I don't mod my cars either.