Questions about rooting a tablet device for making kiosks

My company's looking at the option of using Android tablet for making kiosks. The thing is, the majority of the native settings must be blocked from the user, and very limited apps and utility will be exposed to the customer. From the looks of it, a custom ROM would be the perfect solution, but that requires some arbitrary device be rooted. But then rooting voids warrantee, and this is meant to be a commercial product, so some kind of warrantee is needed. Is there an alternative method? Or what's the legality of commercial rooting?