So, building a "perfect" torrent client from the ground up is a daunting task. But the "good" news is that nobody built such a "perfect" client just yet, so if you have some spare months of your time, you can take a shot at it. Or even better yet, open the issue tracker for one of popular clients or libraries, and add one of the missing features from the list above.
Which of the qualities you listed are lacking from the currently most popular torrent clients (qBitTorrent, etc..)?
Otherwise I'm confused why you mention it.
I hope this will mean that in the long run Firefox (and other secondary browsers) will gain more users again. For me, Firefox is a solid piece of software. Works well in strict privacy mode, with uBlock Origin and Multi-Account Containers.