Hi Glen,
The is no reason why any competent sailmaker should not make a successful split junk rig if they can accept and follow detailed instructions. Note that I have underlined two words in the first sentence.
The Mark 1 rig for Edward Hooper's Amiina were built by his local sailmaker, but I did provide him with very detailed instructions and offsets for every panel shape. It was well made though there were a few slight errors where he had not followed the exact dimensions. That rig was just too big for the hull, our mistake, so when it came to a smaller Mark 2 rig I built it myself with some help from Edward as that seemed easier than writing the detailed specification, and certainly cheaper as Edward only had to pay for discounted materials.
As Arne pointed out many years ago, sailmakers do not readily accept the cambers we junkies use as they are outside the accepted Bermudan range. Modern Bermudan sails are computer drawn and cut so sailmakers really only stick and sew them together. It is difficult to persuade them to think outside their range of experience.
No sailmaker would be prepared to read through all my draft notes, and I'm afraid that the new simplified 'painting by numbers' version is not at the top of my 'to do' pile.
I suppose the answer to your question depends on how good a set of instructions you can provide for the sailmaker/ seamstress to sew, and when you do it is probably easier to do it yourself. Once you have had a little practice there is nothing really difficult in building a rig, and it is an interesting exercise.
My email address is in my profile if you want more information.
Cheers, Slieve.