Is there a basic ratio for dill pickle brine which will be safe for any vegetable?
Essentially, food pathogens cannot grow below 4.0 pH and vinegar is significantly more acidic that that.  If you go here and scroll down a bit, there is a good, succinct explanation.  They use brines of 38 and 44 percent vinegar "for taste and safety".  With this basic information, it would be easy to create brines that are safe and suite your taste. You really don't need salt, sugar, spices or herbs for safety for vinegar pickles (though you do need salt for lacto-fermented pickles).  The acidity alone will do it.  Of course, you probably want your pickles to taste good, so those other ingredients will be necessary.  I should also add, that the site I linked to adds a cook step.  This makes the pickles safe immediately after cooking.  Without a cook step, the pickles will become safe over time, as the vinegar permeates the product, but may not be safe immediately.  It seems that the addition of a low temperature cook step is an interesting innovation that improves safety and the ability to maintain a crunchy product.