Interesting question – but I think it should be academic rather than practical.
I suspect, although physically possibly, it would fall foul of burocracy at numerous stages, apart from sheer postal costs.
The various packages will be too large to mail as ‘exempt’ from Customs Declarations and therefore will attract the attention of Customs on arrival in the destination country and therefore possible Duty, VAT, Sales tax or other charges depending on their local rules.
The frame, with stamped numbers etc, is the ‘identity’ part of a moto to which there should be a matching Registration document. Again Customs might put 2 and 2 together over this unit and take a greater interest.
Once assembled and on the road the ‘home’ Registration should entitle its owner to use it – but there would be no record of its entry into the Customs zone (eg. at EU exterior border or permitted point of entry) which could present problems if ever stopped by Customs (some countries often do have wandering patrols close to borders) or Police. Being ‘undeclared at entry’ might make its use illegal on public roads and/or invalidate insurance.
This assumes it is put together EXACTLY as the manufacturer’s original specification and its internationally accepted Type Approval or local Inspection Certificate, as was originally required to obtain its home Registration document.
As a secondary consideration, some countries have draconian environment and safety rules that prohibit any modification or fitting of aftermarket parts replacing manufacturer’s originals. I hope you do not lose a single washer or nut in the process and even think of fitting a non standard part! Although tourist vehicles temporararily imported may be exempt this.
If 'they' catch you out on one thing, be sure everything they can find will be used to sex-up the case against you.
I would love to have such a bike (again! - I once briefly had an early T120 Bonneville) but would even more hate to have it confiscated and destroyed.
My advice would be to ship it in as a temporarily imported tourist vehicle and avoid all the potential problems.