In previous interviews, I've talked to organizers who have advertised crossover events through their local coffee shop and had to hold three impromptu lessons to accommodate all the beginners, DJs who have repeatedly told me in person that they are playing to the least experienced dancer in the room and others who think that crossover events could be wonderful outreach to get people dancing, and callers who have felt a need to discard some of the more challenging choreography to adjust to the crossover music and the more challenging phrasing (or lack thereof). The views do rather seem to vary.
Truthfully, I've had fun at crossover events with lots of new dancers and ones with mostly experienced dancers and can see a place for each. However, my own opinion is that I think it comes down to intent (and, yes, the organizers do need to make a choice at the outset): if one is going to advertise the event to people outside the contra/folk dance community, then make a point of catering the event somewhat to the new dancers (e.g., have a scheduled, structured contra dance lesson ahead of time; make sure the dances aren't overly complicated). If it's not going to be an outreach event and is, say, a private party to which only experienced dancers are invited, you can institute chaos lines, medleys, and more complex dances (although you are probably going to have to find funding through sources other than your friendly local folklife society).
That said, I personally find it can be a bit more challenging to "direct traffic" to new or lost dancers in the line in the dark; I've found myself revising some of the strategies I use to help lost dancers in a regular dance, like relying more on (gentle!) tugs in the proper direction and more exaggerated pointing to the proper shoulder to pass and the like. It's a different challenge to try and help someone verbally when there are lyrics and calls both to compete with and it's usually a less well-lit ambiance, so they may not even be totally sure of where you are. This is not to say that these factors are insurmountable.
I'm not sure if there's "one true answer" to the question. But regardless, I will make a point of going up to someone I don't know -- at crossover and regular contras -- and asking them to dance, and even if they turn out not to be the most experienced dancer on the floor, I will make a point of having fun and enjoying the dancing experience they have to offer. As one of my very first dance partners said to me my very first night of contra dancing, "Everybody starts somewhere."
I welcome your thoughts! (And if anyone who's going to Chattaboogie this weekend decides to ask those people from the Friday Flourish videos to dance, I have it on good authority that it would be much appreciated. It'll be our first time dancing down there and it'll be a great opportunity to meet new friends!)