Just out of curiousity, how did you arrive at the "139/S76 at the high end, EC135/145 and A109 at the low end"? Is that based on cost, capability, speed, endurance? I'm assuming that is based on $.
If you're planning on landing on hospital roof, have you considered the weight of the 139?
Just back from the Augusta 109 course in Italy. Nice machine...fast, good endurance, IFR, single pilot, fairly pilot proof, able to adjust their machine to fit the customer. May be worth a look.