If you are concentrating on small - medium Eurocopters, then I am assuming you are looking at 350's, 355's, EC120's, EC135's, Dauphins?
You'd be competing against some of the well established 'big boys' and would have to offer something that they can't, with the spares support and tip-top customer service.....definitely a possibility, especially when it comes to customer service.
The idea of 'over-night' servicing is a good one and, I think, worth researching.
I've got to ask also....what general location are you thinking of?