So I asked a few questions about PCBWay's CNC assembly service to see if I could get them to basically make an entire heatblock fresh out of the oven and the response sounded positive enough for me to try it. 

The first thing was to make an exploded view of the assembly, and in Fusion360 this is done though the "Animation" workspace.

I used the transform command to manually move out all the parts so that they're hopefully all visible from this angle and then turned it into a drawing:

PCBWay got back to me and quoted $334.08.

I then tried a few different things to see what the lowest was without assembly, such as increasing the center bore from 5 to 6mm (limited by the M7 on the bottom) and deleting the flat faces, but just the main block was quoted $277.52. An aluminium version was $257.69.

Even if I could justify the price and assembled myself, the additional components is at least £70 ($85) ontop of that, and leaks would still be of a concern. Thus, I'm going to take a page out of Apple's book and look into 3D printing a "unibody" coaxial hotend. I'll say more in the next log, but the idea is similar to the B3 hotend:

I've also been reading the research paper by this redditor and it sounds like continuous fiber support  (carbon / basalt / copper) is an entire project in of itself; I'd rather put that time towards #SecSavr Suspense [gd0105]. Thus, I'm likely to omit the centre expansion port.