Is it possible? Sure, Hentai did it on this very forum...
Is it worth? More complicated question because that all depends on what you're in the market for, what resources you have available to you and whether or not anything on the market fulfills your requirements.
In terms of resources: a CNC machine for metal parts, a degree in electromechanical engineering, some skill in finding suppliers and plenty of money and patience. Now those things all help and you certainly don't have to have them all but the less you have to work with, the harder is to build something that works.
In terms of what you're in the market for: when Hentai built his 12 inch full range field coil, he did it because there was nothing that really fit that that came off a shelf. Same for Solhaga and his AMT, no commercial AMT reaches to 300z but he wanted it and so he built it.
My school just picked up a CNC machine and 3D printer, so I may try something with them in the near future. If I do I will try and remember to report back to this thread because right now I'm seriously thinking about making (or at least trying to) a 1 inch exit compression with a CNC machined aluminum diaphragm like YG uses and a plastic body printed in 3D ( that's where I got the idea...), but anyway this all goes to my point on resources.
i am on the team that is responsible for building both the machine and printer, so I can tell you that this stuff cost some serious cash, as in 10k for the CNC machine (think its three axi) alone.