A 500k log volume, a 250k log tone wired as a master tone, and a 500k log tone as a blend pot would get you all the combinations you want.
I attached a schem to illustrate the blend function. If the blend pot is turned up full you have the normal selector function with the 5-way selector. Turning up that pot adds the bridge pickup to all settings on the selector including the neck pickup, and adds the neck pickup to all settings on the selector that include the bridge pickup. It is what I use and find very comfortable.
Cheers Stephan