Yes, complications do come in when trying to conform to differing regulations - it is possible to cross over with exceptions though and teams can exploit that.

In theory the bare bones of a modified touring car for Rallying shouldn't be any different to road car modified for rallying. There shouldn't be any disadvantage here and it bring a whole new level of interest to the sport in regards to the fans.

Yes, teams want to win but equally they want to make money. In today's day and age, Motorsport needs to consider things like cost, reliability and sustainability (environmentally), it creates a very bad image if not. If a car can go over and beyond then surely that promotes a healthy image to the team and thus the car that carries the manufacturers badge.