It would be very much easier to do a Linn and either buy in the bits for a simple screwdriver job or get someone like AT to do body A with windings..
Linn don't build any cartridges and never have. Nor have they ever built a budget tonearm.
Rega obviously buy in most of the parts they use but everything is assembled in house. I believe they own a plastics molding company, which is quite a clever move.
A P8/Exact has to be entry level high end imho.
Hard to define I suppose. Fair to say that all of Regas turntable products punch well above their weight. Except the Bias maybe, which I do not like or understand.