Harness/Roll Cage

[malteseracer]

Im looking into a Mini Cooper S or a Clubman S as my first car. With 30mpg and the ridiculous resale value, the price isn't the issue.
Im running road rallies all summer (no speeding, just fun little 100 mile trips) and other stuff like that and i wanted to know about the warranty.
Lets say i put a racing harness in the two front seats just because it's cool or a roll cage just because i can. Would Mini really frown on that?

[bad venge]

I've taken mine in with four point harness's and a harness bar and they never said a word