1, 2 and 3. Yes.
4) It depends on which bike and what I'm doing / where I'm going. Arriving with things wet or dirty is a frequent source of annoyance this time of year. (Things being typically tools, spare clothing, wallet, keys, phone, Ventolin)
5) Attachment to bike (related to security and stability)
6) Light mount, definitely. Reflective elements possibly.
7) Medium? Around 5 litres mostly works for me.
8) Grey or black. Just measured my favourite saddle bag - rectangular(ish) box at 20x20x12cm.
9) An internal loop for securing items such as keys for house, car & bike lock. Internal pocket with an additional closure would work equally well and also hold a wallet & phone.
10) Permanently attached is only ok if there are no high value contents - detachable with a carry handle / strap (or maybe a removable inner compartment) often makes more sense.
You might think how to present the answers to 1, 2, 3, 7, 8, 10 as percentages or in graphical form to justify your conclusions: qualitative answers (4, 5, 6, 9) can be difficult to analyse when there are enough of them to make a survey worthwhile. Don't spend too long on research because making and testing a prototype will take more time than you can imagine! Good luck with this.