Lots of good advice so far. Ownership is pretty much the only way this will work in practice to have the required short-notice availability. Plus an owned aircraft is a known quantity in terms of operational safety and maintenence condition. Even a 100 kt plane will beat the tar out of driving. Now for the wet blanket. For better dispatch reliability, you will need an IR. And even with the IR there will be occasions where the trip will not be possible. And if you are on a strict timetable, the chances of weather getting you on the outbound or return trip is higher. The one advantage you have is that the trip is relatively short, within the same local weather conditions.
I used my own aircraft to do relatively regular weekend commutes between DC and home in Central New York when I was temporarily working at NIH. There were seasons, like mid November to mid-April when this trip was rarely doable due to ice and/or weather on the desired travel days. Even with 1 day flexibility on each end of the trip (which I could exercise) it was not always possible to make the trip by air. But when I could, it was gloriously better than driving 7 hours. Between May-November, I could make the trip about 50% of the time on the desired dates. Time to spare, go by air...
