If this comes to fruition, the date and the location would be figured out as far as possible in advance to give everyone time to adjust.
And if the date is on top of something (there are only so many weekends in a year as we hear over and over), maybe as a group the local racers could lobby with those in charge of scheduling the conflicting date event to adjust their schedule. This race is unique as we would have to look at the schedule nationally to find a date, maybe a regional race/divisional/combo could change easier. We might need your help "negotiating" with your local event holders. This can be done, especially if you have numbers behind you.
It's hard to find a date that works for 500 racers from across the country. But if this thing happens, we will do our best.
Anywhere that would be "fast" might also have issues with weather. Can't do this too early or too late in the season as some racers aren't ready yet or have already "blowed it up" for the year. Only so many weekends in a year. Need room for national event parking capacities, hotels nearby, etc. If this thing happens, a lot to discuss. Who knows . . . .