Ok so first off, thank you for the replies.

Looks like I've got a huge amount to figure out and get planned in. Im more of a figure it out on the fly than a planner kind of guy but I understand the need for it in this situation so I'll get my head down.

In terms of size, what sort of frame footprint should I be looking at to begin with and will I be ok with the 80 x 80 x 5mm steel box section, can I go smaller or do I need to go bigger?

In terms of creating more mass to remove or dampen vibrations, is this why some machines will have additional weight added to the machine?

I don't have an issue with sourcing from China. The previous small builds I have done have all been China sourced and we have imported machinery before so we understand the process.

Forgive the confusion with the 100mm blanks, imagine doing a 2.5D carving or a mountain. That's close to what I'm thinking of, apologies I can't give out more of an idea. Sort of like a thick relief carving.

You right in the sense that I have little experience of big machines like this. My engineering side is fairly on point for what I understand but more than happy to take on board the comments 're the belt drive. What sort of size belt would I be looking at, they must be wide! Are you thinking of the usual single belt or would it be doubled up, is that even worth it? Do the issues with belt stretch still apply? Would it be better to look at an ally extrusion gantry to keep weight down if I'm looking at belt drive? Will belts not chase additional issues in terms of machine rigidity or am I over thinking it with the applications that I'm looking at?

Thanks again for taking the time to reply, I'm super excited about giving it ago but at the same time trying to keep the focused at what appears a mountain to climb lol.

Apologies for any spelling mistakes, I'm writing this out on my phone so autocorrect loves to kick in.