A lot of this depends on your personal flight experience (and I mean EXPERIENCE, not ratings)
If you're a private pilot and don't have crew time in a turbojet, I would not even consider SP jet ops on a waiver. My gut feel would be to get 1000 hours crew time first. Obviously insurance would require some supervised OE in any event.
250+ hours/year, combined with what I assume would be an insurance-mandated annual trip to flight safety should be sufficient to MAINTAIN proficiency...acquiring said proficiency would depend on your existing flight experience. You'll want to fly as much as possible when you initially acquire the airplane...most folks will tell you they don't feel completely comfortable in a new jet until they have 1000 hours in type.
Personally I would feel comfortable doing SP jet ops, but I'm an airline PIC with multiple types and thousands of jet hours.