The 6.5x378 has been done already, can you say diminishing returns? Hill Country Rifles has decided to not do anymore 6.5x300 Wby's as they can't guarantee the accuracy, I believe they will still do the 26 Nosler. This is contrary to the older wins at 1,000 yards with the Pennsylvania shooters in I believe the 1960's or 70s. Few shoot them now.
Anything smaller than the 7mm STW seems cantankerous to work up loads for, this is from what I have read, no first hand experience.
