Evoque Security- second immobiliser?

Got stopped this morning on the way to work by plod as another Evoque in the area went missing last night and they were just checking it was mine..

Given that this is still a massive issue for keyless entry cars would there be a problem with the current warranty if a separate immobiler was added?
(If you remember back to the 90's where car theft was so endemic where the use of secondary immobilers was warranted) what would be the issue now in getting on added?

Has anyone gone down this route?

Thanks,

J