First you need to find out what the boss MUST have. Speed, Lav, standup cabin, etc. Then find out what he would like to have. I would suggest that you don't try to fill all the 'would like to have's'. You will end up with too much aircraft. Once you get beyond 9 passenger seats the size and cost of the aircraft increases dramaticly. How often does the boss want to carry more than 9 passengers? If it is once in awhile, make two trips. Basicly, you have to make and keep the boss happy. If he' shappy with the aircraft, things go smoother.
Also consider that when companies get their first aircraft, they tend to underestimate their usage. I went to work for one company that programed their usage at 400 - 500 hours a year. The first year, we flew just under 900 hours. Companies tend to find uses for their aircraft that they had not considered. You might want to give consideration to two aircraft. A turboprop for the shuttle, like a KA200. And a jet for the longer range missions.
I would also consider stay a far under budget as possible. Too many coporate operations have been closed over budget issues. Being under budget makes it less likely. Not impossible. Just less likely. But most important, keep the boss happy and keep him part of the process.