According to this story, many challenges to mainstream major party presidential candidates will not be resolved by the time Illinois must print ballots for the primary.
Illinois could save itself this headache if it abolished mandatory primary petitions, which a majority of states have done.
It sounds like each county can set its early voting period.
If the early voting period were set by state law, then it is more likely that the filing deadline would be set in order to provide time for challenges and their resolution, prior to the creation of ballots.
In Texas, challenges must be made shortly after the filing deadline, and even lawsuits must be filed before voting actually begins.
In re: Donald J Trump, et.al.
Trump is being invited as a necessary party with unique standing as a public officer sworn 2016 CINC POTUS candidate on the ballot of every state primary or caucu — and in this specific case Natural Born Citizen registered voters not enrolled in any ballot access party petitioning to join on the party enrollment lock-box USCA2C original proceeding requesting certification of question under SCOTUS Rule 19 allowing Trump to invite his New York State followers not enrolled as GOP into the April NYS CINC POTUS GOP primary.
See Rosario v Rockefeller 1973 SCOTUS docket 71-1371
and
Van Wie v Pataki USCA2C 00-7379
Cruz NBC eligibility crisis has developed since enrollment lock-box closed October 2015
Only Trump the resident New Yorker and lead GOP candidate has the standing to force this issue certified question successfully upon SCOTUS