Definitions are important!
Good for you for realizing that and wanting to get clarity before calling for entries.
I get frustrated as often the definitions are not clear ... and interesting enough, what it might mean at one Fair/Show may be different at another ... and different again to the Judges!
I've seen classes mention "traditional" ... and it leaves me wondering, so if I use a traditional pattern, yet use Kaffe Fassett fabric, is it included? Or what about a OBW? ... certainly not an oldy goldy, yet the piecing technique is certainly all about historical quilting!
And so on ....
Then yesterday, I called about a class I'm thinking of entering and wanted clarification. No real answer came forth ... and it was ended with, why don't you go ahead and enter? after all you have nothing to lose! Well, um ... I do like to know I am in the "right" class and do not want to be disqualified!!!
What about seeking your guild membership's input? At a meeting, pass out a questionnaire and have them write down their definitions and ideas. To encourage participation, offer a lucky draw of those who submit info ... though give them a separate ballot, so that they can remain anonymous with the feedback, should they choose. Then later on, sit down with a cuppa (or six!) and try to figure out the puzzle! Perhaps the class will not be called "modern" quilting ... but something else?
I don't have your answer ... though some other things that might "fit"
* inclusion of alternative fabrics and materials