Our signings are now predominantly data led, with a focus on value for money, supplemented by 2-3 that the manager has seen that he believes will fit our system. As we have a foreign manager, that supplement will be foreign rather than Scottish (Devlin, Shinnie etc) for the next window or two. That should revert to Scotland again as Thelin becomes more intimate with the players here, and his knowledge of home becomes less up to date. The exception was Nisbet, but that was clearly pragmatism based on Miovski leaving and the realisation that Ambrose wasn't actually a professional footballer at all. I agree, I would like to see more Scots.
I don't think that's necessarily the case at all. I would say that the majority of the signings we make of any nationality rarely stick around. Obviously we can really only take this century as relevant, because of changes in transfers that probably didn't properly unfold completely until the late nineties. Of the Scottish players (Several, Nicholson) we've signed, there are just as many that play 100+ games as there are foreigners such as Logan, McGinn and Hayes*. Guys like Kenny MacLean had no more affinity with Aberdeen than Arnason for example. The main criteria for a player staying any length of time at AFC is if they fit in at our level, rather than nationality. MacLean was our level when he joined, but moved beyond that eventually and so joined Norwich. Miovski stayed another year just like Ferguson. I can't think of a single player who has joined us and stayed beyond the point they were deemed too good. If a player finds his level here then we'll likely immediately want him replaced with someone better as we're fickle that way! Devlin last season regularly identified as a weak link, Shinnie too, after a handful of poor performances.
In terms of Scottish players in the squad, the most disappointing area is youth players coming through. Ramsay and Barron probably don't help the numbers, but I'd have hoped we'd be targeting one to two players per season making the squad and get regular minutes before the age of 21 (a bit arbitrary, I know). Milne squeezes in (defenders take longer!), and Duncan should be aiming for next season or moving on. I think youth products are really the only ones that are likely to develop significant affinity and loyalty, and the most likely to see a good number of appearances. Mainly because they might have family in and from the city, and may even raise family here. Again, though, that's only if they find their level here.
*I've assumed you class Brits and Irish as foreigners (I do) based on your comments about the national side.