Jack Keller’s instructions on how to make yeast starters
(http://winemaking.jackkeller.net/feeding.asp) suggests that a total of
less than a cup of must/juice should be added during the starter’s long
time of creation. I realize that his instructions are based on a
professional's advice, but how different would it be to make the
starter, add a cup of juice, and pitch the next day? Is it worth the hassle?

Is it possible to do like above, but add all of the syrup (diluted) you
would normally add to the juice/must? I am wondering if I could ferment
the syrup’s sugar first and delay the time my juice is exposed to the air.