I'm guessing that it was meant to be premier and division 1 but East Lothian didn't want a predominantly northern division 1 and perhaps Moray Titans didn't want a predominantly central premier.
Guess the ambition has to be a national premier and then north and central below? Thus new Central clubs wouldn't be in at the deep end Edinburgh A would be somewhere more logical
The problem is that Scotland as a land mass is relatively big, and this involves a lot of travelling if you have a national structure. Ideally we would have a more regionalised structure - Central and Northern, or even West, East and Northern - but then we face the same old problem facing rugby league in 'emerging areas': teams want fixtures at their level of ability, but they also want them in their locality. At this stage of development, the weaker clubs aren't capable of travelling the length of the country week in, week out. As the better clubs become stronger and more stable, and clubs starting second strings is very positive, then I could envisage a national league stretching from Aberdeen to the central-belt. What is needed, though, is for enough teams below that standard to create reasonably-sized regional divisions.
So, yeah, the structure you describe has to be the aim. Until there are enough clubs around, though, the league structure is going to be the sort of compromise we have this year.