I'm not a frax pilot but I have looked into these same issues, because I also put together a business proposal for a regional fractional program. If I remember correctly, deadheading accounts for about 30% of the flight time for frax aircraft. That was a number for one of the big operators, I cannot remember which one. Of course is only really an issue if you're planning on only charging the hourly fee for occupied hours. You could set it up where they pay the hourly fee for deadhead too.
As for lead time, I believe the frax operators guarantee an aircraft to be there within 4 hours after the call is made, depending on aircraft type. It's probably longer on the big aircraft due to the obvious limited number.
For large charter companies with aircraft stationed all over the country, they might guarantee a lead time, but most smaller charter companies will just tell you when they can be there by, and if that's good with you, then you're rolling. If not, then you have to find someone closer. (If the charter compnay is worth its salt, then IT will find someone closer to you, of course)
As far as charter companies go, it doesn't really matter to the charter operator how much deadhead there is, because usually the customer pays for any deadhead flights, so from a business standpoint it is all revenue hours.
As a side note, Frax operators advertise that you only pay for occupied hours, i.e. the time you're in the aircraft. Well, we all know that it costs something to reposition aircraft, and therefore those costs are passed on to the customers, albeit indirectly. So you DO pay for deadhead time, it just doesn't feel like you're paying for it. What ends up happening in the end is if you live close to a major city, then the time taken to position an aircraft for you is likely to be smaller than to re-position an aircraft to someone who lives way out in the woods. So the result (since the cost of system-wide repositioning is passed onto you, as a customer, through high monthly fees, or high hourly fees) is that you end up paying for part of the country-bumpkin's repositioning time. However, the convenience of being able to call and have an aircraft on your doorstep in a guaranteed 4 hours will be seen by many as worth the extra money involved in getting into a fractional program.
Ray