But first, let me say, *I* have not had any of the problems you have referenced with regards to trading...I have never had to enter trades more than once, all my trades seem to go through without any problems, so I'm not sure if it's unique to you, your computer, etc.. perhaps others have this problem as well, but I never have.
Now, on to a couple of your questions: Why do they not offer a "flip" button? This question has come up numerous times over the years (I've been here 10), and the answer is always the same: "It's to prevent manipulation of stock prices." Basically, if I could flip stocks back and forth, it would be easier to skew the prices. Maybe not so much now that commish free time is gone, but if you ever opened your port on a Saturday after commish free time started, you can imagine how your port would bleed if people could 'flip' stocks back and forth with no problems. MAYBE now that commish free is gone, having a 'flip' option might be a possibility?? Let's wait and see - but now you know the reason we have not had one till now.
Why can't we buy stocks at the same time? See the answer above ^^^ Basically, it prevents manipulation of stocks. You may not like the reason, but that's been their answer in the past.
Your other points are up to HSX and how much time & money they can spend to code the site to do what you are suggesting....remember, the site is FREE, and to do many of the things you suggest continues to add coding and expense to maintain the site, it may or may not be within the range of their budget constraints...it's something HSX will have to answer for you.