TBH, this sounds like a crit, minus the closed course and all safety considerations. IOW, an impromptu alleycat race.
I've watched a local fast group deteriorate from a fast but safe club ride to a free-for-all alleycat crit. Warnings and even tickets from cops didn't change their practices. The former club leader tried to punt responsibility for the A group ride to the local pro team. The pro team wouldn't have 'em.
I've watched the local pro team ride, since my neighborhood is along a popular training route. The pros are very fast but not reckless. They usually do roll through stop sign intersections -- carefully -- and slow-and-go through traffic lights where appropriate. But they don't heedlessly blow through intersections or surge to drop people off the back. It's a controlled paceline and team ride, usually no more than a dozen regulars.
There's no way to keep a group together when the front of the pack blows through intersections, and surges to drop the pack. Anyone who hesitates even slightly to watch for traffic is never gonna get back on unless they can cobble together a group of three or more strong riders to close the gap.
Not my cuppa but knock yourselves out. If I were younger and stronger I might think it was fun once in awhile.