Not 100% sure what you really are complaining about because Memory cues working like they always did and how everyone knows how to use it. Turning it upside down could be an impact for many more people than helping others. But this is your opinion and this is fine.
Let me comment to some of your arguments.
You ask for a way to promote hot cues to memory cues. This could be a nice add but be aware that there is a way to promote memory cues to hot cues. If your workflow to manage your cues starts with creating memory cues, you can convert them to hot cues easily in rekordbox. It is a function in rekordbox for a while now.
The way for automatically create memory cues when a hot cue is created, I wouldn't like all the time as I am not always have memory cues and hot cues in sync. It would need to be a setting the user can decide on. In addition this would need to be added to all devices by firmware update if this makes sence because users often add hot cues on their gear as well. It could be an issue when there a no slots left to create a new memory cue as you don't want to delete another automatically.
Regarding the waveform countdown you are correct. However to have 2 countdowns could be confusing for DJ's. It would have to be marked clearly if it would be for memory cues or hot cues. But as hot cues are instant, what is the benefit to know when the next approaches?
Memory cues are chronological sorted from the beginning. It is the hot cues which aren't. Not sure I misunderstand your ask.
I disagree with your assumption that there is only one cue needed. It goes back to the preferred way of djing. Therefore it is good to have both ways. If you want to use hot cues only - use hot cues. If you want to use memory cues only - use them. If you want to use both - you have the option. Taking away one of them is not a good idea at all. Btw. in forums of the competition where only hot cues are available there is an ask to add memory cues on top.
If I would predict how memory cues and hot cues evolving in the future, I would assume it will go into a direction how the Opus Quad is using them. But this is just my opinion.