3D printing technologies in consumer printers - what's our progress right now?

To those up-to-date about 3D printing technologies, I'd like to know where we're standing in terms of consumer printers - what companies are developing them, expected arrival to printers, etc., and technical challenges in achieving them.

I'm interested in the following features/technologies:

- Variable-diameter nozzle: I haven't seen any. I haven't heard anyone talk about them. I think it'd be a great thing to have. I understand there would need to be moving parts and that nozzles apply pressure on plastic to extrude it, and there needs to be consistency to extrude the plastic in a certain diamater - beyond needing to heat up, of course. Right now it's achieved with solid pieces that apply pressure just due to the materials they're made of and their geometry (ignoring the fact the plastic is pushed into them and heated, I assume there's some assist by gravity). But why not split them into parts, machine them, and use electromagnets or mechanical parts to push and pull them to create the desired diameter? I've already seen similar designs, just not in 3D printers.

- Built-in filament recyclers: that's a matter of incentive - companies don't have a financial incentive to make them unless they're sold as a product due to filaments being consumables, so when they're consumed if people want to print their options are to get more, usually from buying new ones, or recycle. There's also the difficulty of separation into types of plastics for various reasons. So has any company been able to create a sustainable financial model to make recyclers and have any plans to integrate them in printers?

- Built-in filament combiners - again, same idea with the filament recyclers

- Move to pellets - why did spools become popular to begin with and why is there no commercial move to pellets? Is it because filament spool makers make more profit from selling spools vs. what they would if they sold it in pellets? In more traditional manufacturing with plastics, injection-moulding, pellets are the standard form plastic comes in, and their costs are much lower. I've only seen DIY and individuals' versions of transforming existing printers to use pellets.

- Inductive heating - I've seen 1 printer that uses it and the technology itself isn't new. Why isn't it more widespread and how quickly is getting adopted, what plans are there in putting it in more printers, etc.

- Multiple axes heads - more advanced machines have them, I've seen various individuals make them, while I've seen in machining things other than plastic (mainly in cutting metal) machines that can move in 4 and even 5 axes - so same questions about this as well.

I think having all these technologies would make 3D printing faster, cost less, enable us to make more shapes and in that way will also be more attractive to more people.

Feel free to share more technologies that might be integrated in 3D printers in the near future and share where we're at with them as well.