I am always welcome new ideas but most of your ideas create more work and a lot more complex to achieve. I don’t think Blizzard will do anything about it. The only thing I like is having all 3 followers follow you if you play solo. The rest like primal shards, more recipe in the cube are not so realistic.
The worst idea is having other class of your as followers. You have got to put in effort to farm gear for the class that you are playing. What you are suggesting is a bit lazy and asking Blizzard to create bot for the rest of your char. This is definitely not going to happen in any game I can promise you on that.
They haven’t even improve the current system which I am not going to mention again here but I have posted here a few months back about 10 things to improve on this game which I think is more realistic to achieve and even then some of the stuff I requested will never going to happen.
The game is over 8 years old now and there are a few flaws of course but Blizzard won’t spend more time or money to create more complex system. Probably some minor adjustment and some improvement on quality of life like Pets picking up Mats and DB. They probably invest more into D4 and hopefully learn from the experience from D3. That is all we can hope for.