Hej Ljungberg,
Sorry, I think you need to lower your requirements or specify better. It seems that you want to do everything with your machine, and perhaps there is one to do that job, but in that case it must be pretty expensive. To work with steel you will need very low RPM spindle with very high power, to work with wood or other soft material you will need very high RPM, high feed rate and not that much power. To print 3D you need very high feed rate and at least a fourth axis (filament feed). Alu can be milled dry, but steel not, and wood must be cut dry, so even the way you'd handle cutting fluid must be considered.
Cutting and engraving works, but if you want 3D engraving of complex pictures or objects than you will need very high feed rate and RPM also, otherwise it takes forever, so a belt driven stepper, or servo driven system may be necessary. Servo driven system would be the best but is too expensive. So, I think you need to set up a priority list, what is MOST important and everything else should be regarded as bonus. I think you want too much from one machine.
But... I don't know everything, so perhaps I missed something.
I designed and built my own machine, it can cut and engrave wood, plastic, alu and brass/copper and I am planning for a 3D print head as well. I think if I wanted to buy my machine I would have to pay over £3000. It is not optimal for 3D printing because the feed rate is maximum 8000mm/min currently, but it is better than some cheap 3D printers have so it will be good enough for me. I would not even dream about steel or any other hard material which requires cutting fluid, low spindle RPM, low feed rate and very high power and rigidity. My machine weights only about 90kg, made mostly of aluminium, so it is not for steel. Anyway, it is not for sale so it is not for you, just saying to demonstrate what you can expect. Have a look around on my blog if you are interested in seeing it. There are plenty posts about the details.