Arranger keyboards have always been made for the Hone Hobby Player so the chances of them fitting features that are needed for live play is pretty small. (The last thing you want is to override a sound without warning etc.)
Some of the features you mention (Like registration cut off etc.) have been standard on other keyboards since the 80s & 90s, so can’t see why they could not add them.
As for the keyboard size, then ever since the Tyros came out most SZ members (And many other potential owners) wouldn’t buy one because they didn’t have 76 keys, so they probably won’t go back anytime soon. (Not enough demand to produce 2 models (Like they did with T5) as arranger sales are sliding down at an ever accelerating pace and will soon become niche like the home organs they came from)
The glory days of arranger keyboards are over, so make the best of what you have got as there may not even be a newer model in the future. (Although I think the market could take one more)

Bill