E85: E70, E74, E80...changing pump mixture a problem for tuning?

[scheides]

See this is the problem with a good idea like E85, they go and screw it up like this...yet still, the rest of regular gas receives up to 10% ethanol through the winter and it doesn't seem to bother anyone?

The only thing I can think of is to get tuned for E70 and then as you pump in the various other mixtures you will simply be running richer. This would theoretically be more safe than getting tuned for E85 and then running that tune on E70.