Bucket of cold water time, I'm afraid
I've been into this in depth with one of the UK magazines, and discussed it with others.
The basic problem is that the circulation in the UK only would be most unlikely to be sufficient to provide a reasonable profit for the publisher; at a price that would not be too far from the existing UK mags.
Yes, of course, if the worldwide potential could be exploited, then it's virtually certain that a circulation of 30,000+ could be achieved, that being around the minimum figure for such a venture to be financially viable and stable.
But the problem is then also the substantial marketing costs of accessing all those markets, - i.e. USA, Canada, Oz, and New Zealand; never mind that N America is already partially at least catered for via periodicals such as The Highlander, and a few others. which have regular Scottish genealogy/family history articles.
Australian interests are already reasonably well provided for by the magazines of the state and local FHSs; ditto in NZ via the journal of the NZ Society of Genealogists.
A further aspect is that many folk in Australasia already subscribe to one or more UK mags, and many would want to continue to do so, given ancestors from all over the British Isles, so that that proportion of the market would need to be persuaded to pay out another, say, Oz100 or NZ$ 120 for another annual magazine subscription might not be that great.
Given that the existing 5 UK genmags have lots of generic articles, e.g. occupational, research techniques, etc., that also apply to Scotland, the question arises of whether there would be sufficient content left to support even a bimonthly or quarterly periodical aimed purely at the Scottish scene, without the need to compete on that generic content with the other genmags.............
David