Re: Looking for new breeder queen stock to try
Your basic stock is derived from Carniolans obtained from Glenn crossed to local feral survivors from your area. This suggests NWC as a good entry point, however, they probably won't give much hybrid vigor.
Mike Palmer's genetics derive from Carniolan and Buckfast. I second the suggestion to get some queens from him. They are winter adapted and have the other traits described.
My personal suggestion is to get some Buckfast from Ferguson in Canada. If you order them now, they should be delivered next June. They are adapted to northern climates, will mix fairly well with the genetics you already have, and have been selected for hygienic behavior which helps quite a bit with disease resistance. The negatives are that they often are a tad aggressive when crossed to other lines and they are not very resistant to varroa. The aggression can be toned down by 2 generations of selection. Otherwise, they are superb honey gathering bees.
The only other suggestion I can make is to get some queens from a source that has bred specifically for mite resistance. You probably have an idea of the suppliers who have done this type selection.
If I were you, I would probably get a few NWC, Palmer, and Buckfast queens and set them up in separate apiaries until you see how they perform.
NW Alabama, 50 years, 20 colonies and growing, sideliner, treatment free since 2005, 14 frame square Dadant broodnest