I've never been much for fancy push mowers. Just a simple lightweight manual start push mower is all I need. No drive components to wear out, break or require adjustment, plus the drive system usually adds substantially to the weight of the machine. I prefer a light 60 to 70 pound mulching mower with ball bearing wheels. The light weight and the smooth rolling wheels make self propel unnecessary for me. I'm also relatively tall, 6' 1", and have never had issues with the handles being in the wrong position for me, but a simple adjustable handle to accomodate people of shorter stature would be a bonus for some people. Cut height adjustment by way of a single lever would be much appreciated by those who need to adjust the cut height often, but what homeowner really needs to do that? Set it at whatever cut height suits you and leave it there. As far as key start, I think a simple main on/off toggle switch to allow or interupt the power from the battery coupled with a push button start switch would be better because a replacement switch, if needed, would be cheaper and there would be no worries about lost or damaged keys. I miss the old mowers that you could walk away from and leave running. There is wasted time and energy with the newer mowers that stop as soon as you let go of the handle. I know its a safety thing dreamed up by lawyers to protect the manufacturer from being sued by people without any common sense, but it still irritates me. A blade break to disengage the blade and leave the mower running would be nice if it could be done without adding a lot of weight. I keep a clamp on my mower handle to clamp the dead man lever down while I'm mowing, then if I need to step away from the mower to go refill my water bottle or something, I don't have to restart the mower when I come back. Also, I expect the mower to have enough power for its features. If you intend it to bag clippings, give it enough horsepower and torque to effectively shoot the clippings into the bag without clogging up constantly.