I don't actually know what point you're making, that's the issue here. Originally you said that you'd like to see us sign more Scottish players as they tended to stay longer, and you mentioned the national team. I assumed that you meant actual Scottish players and I suggested that there was no evidence that players signed that were Scottish stayed longer than those that weren't.
You then moved to include British or English speaking foreign players, and I suggested that there still probably wasn't any evidence of them staying longer, given we've had a million English players who've come and gone this century.
You're now talking about "true" foreign players, and I've no idea what that means.
If it helps, I'll clarify what I'm saying. I would like us to sign more Scottish players as we are a Scottish team playing in Scotland and I believe that should carry some identity (for no real reason if I was being honest with myself).
I believe that a portion of our signings should come from teams in the SPFL (Premier), whether Scottish or otherwise, as I believe that they have the best chance of success as they are the lowest risk of signing (we know they can perform in our league). I think that the manager should be able to identify those particular targets.
I also believe that you are significantly more likely to make a mark up on a player out with the SPFL, but the risk that they cannot perform in this league, is greater. A proportion of our signings should go down this route with a view to it being the quickest way to increase player budget via player trading.
The proportion of the above should vary from season to season depending on availability of good players in our league, but I'd like to see us picking up at least 2 low risk signings from other teams each season. I'm not concerned by Thelin not having that knowledge for a season, and would count guys like Nilsen as equivalent to Devlin, but with slightly more risk attached.
In response to your last three years point, foreign players were in the minority until Robson really. You mentioned Glass, which is why I brought up Gallagher etc. Goodwin was majority British (Stewart, Richardson, Morris, Clarkson etc), Robson signed Pollock, MacDonald, McGrath etc, before the move to foreign based the following window. We didn't sign anyone in the January (Hoillet) and this summer we've gone foreign again. Basically two windows of majority foreign imports, with a similar success rate to previous.
I don't think any of what I've said has any bearing on length of time a player stays at the club. As I said previously, I think that has everything to do with family arrangements and if they've found a level that suits both us and the player.