"I have some that have some Russian influence as far as survivorship goes, however, they do not display the degree of aggression that pure Russians are know for."
Pure Russians aren't known for aggression. I think that has come from sellers claiming purity when in fact they were crossed causing the aggression.
I'm not sure where this is going?? There is only one source of Russian bees to my knowledge. And that's from the USDA. They are not going to get any more "pure" than that. And only if II is used from that point of release. Unless you follow the program that they are using to maintain the lines, then you can only start inbreeding. Increasing diversity isn't an option, decreasing it is if you are looking to mask a trait.
Aside from II purity has no course other than diminishing return. Is that a bad thing? Not in my opinion, but it does not support any theory of purity.
Grading for purity and grading for traits have nothing in common in my estimation. If pure is what you want for whatever reason then so be it. If specific traits or a wide range of traits are your preference then choose accordingly. But simply crossing bees randomly is going to yield random results at best. As Micheal mentioned with repeatability, that isn't easily obtained and unless II isn't incorporated somewhere along the line it isn't sustainable. And then you wind up full circle in the maintenance of a line in the same way that purity of the Russian bees is maintained.
But then what happens when the next threat comes along and the line isn't capable of coping with the threat? You make changes or introduce traits from another line. But, which is possible when purity isn't an issue.
"Success is not final, failure is not fatal: it is the courage to continue that counts." Winston Churchill