DR. I am sure your 4 conditions could be met in various parts of Scotland.
Clearly it is like pushing a boulder uphill if someone plants hundreds of Carnica colonies near you one year followed by hundreds of Ligustica the next.
The advantage we have in Ireland is that in the North there are no commercial beekeepers and in the south the commercial and semi commercial beekeepers mostly use native stock.

Starting with hybrids or mongrels could certainly lead to a better bee. Brother Adam demonstrated that you can tinker and improve.
The thing is though, it has to be done in a controlled fashion and what you have with the commercial beekeepers in Scotland is total chaos with regard to stirring up the gene pool. It will never stablise to produce a population which breeds more or less true for the traits you want if there is a random injection of new genetics every year.