1. Bicycles are not dangerous in the grand scheme but they could be safer. I'd go for preventing capsize or armoring against crashes. The former, Shimano has introduced ABS for e-bikes and though I don't think many of us have tried it yet, it's coming hard, finally. Canyon has a spring thing that re-centers the steering and reviews are mixed. I found it laughable at first but then had a good think and now I believe they have only just begun to explore the trade space it gives them to tune the steering feel. As for armor, if half of people aren't even going to wear crash helmets what chance do you have to sell them shoulder pads and hard gloves?

2-6, 11,12: I am not interested in a flag. Bicycles are tall. The biggest menace to cyclist visibility is cell phones. Drunkenness is also cited, but when I dug into the topic on motorcycles I discovered there is an enormous bias to Friday and Saturday night that isn't really relevant to my bicycle commute. If you are imagining some sensor that needs to go on a mast and want a flag for an excuse, put it on the helmet.

8. Be courteous
9. Us-vs-them attitudes promoted by bullies who crave leadership, leading to incidents like the "coal rolling" 16yo a year ago who accidentally crushed four of his six targets and the local cops who initially shrugged it off and let him go. Inattention by comparison is like the weather. I can't control it but it's not actually hunting me.
10. Floodlight on the handlebars, spotlight on the helmet, blinky on the rear, reflective stuff, stay warm and dry

13. Male, 45, 95630
14. Have you identified what's actually dangerous or are you selling to a feeling of danger? And if it makes you money is that ok? Is there a market for this thing? Commuter cyclists who spend extra money on it are a subset of a subset. Can you make enough money to support a business or is this a product for an existing business? The medical industry has a lot more money than cyclists to spend on doodads. If you want to make a lot of money you need to sell a lot of something (soap, shipping) or something expensive (Teslas). If you want to be really rich you have to sell a lot of something expensive (iphones) or create anticipation of it (Teslas again).