I think mostly of training aircraft when I think of small helicopters. To improve them, there should be a FDR of some sort that creates a very complete record of the previous flight. Use it for debriefing and confirming that limits weren't exceeded.
Training aircraft should have training limits that allow the student to fly the entire syllabus safely. There should also be the 'other' limits for when the student screws up. Build this into the aircraft.
Going away from the non-training side of light helicopters, I say set everything up to be as single person operation as possible. Hands on C&C, single point refuelling (and open cell just in case), avionics designed for same, baggage and tool capacity for self-deployability, DI's made clear for pilots (ie: panels located right in front of things to examine, fluid level gauges idiot-proof, etc.)
The other thing I always wonder would be a benefit would be self-levelling skids. I know, it seems kinda weird, but if you could control the angles and heights of the skids, maybe split them for even more control, and all without a weight penalty, maybe off-levels and rough area landings would be more safe.
My ideas come from seeing, reading and/or hearing about small helicopter accidents. The number one cause is human frailties (I'm cautious to call them all errors). Procedures, training, and watchdogs NOT helicopter design is what we really need to fix that.