I think your theory makes sense, except I kinda think cops local, state, and Federal, were waiting there prepared to sniper-fire and take-out COSSACKS.
According to reports, only one of the 9 was a Bandido ... and even that's in question because the now-dead Purple Heart Marine Veteran J.D. Rodriguez apparently belonged to ZERO club (not to mention had zero criminal record in Texas), and whatever MC clubs he'd belonged to earlier in his life no longer existed.
So you supposedly have Cossacks and Bandidos shooting it out and the cops chiming in afterward ... and only ONE Bandido is among the nine dead? ALL the rest are Cossacks, except for shooting a guy who had zip to do with either club? I guess the Bandidos were remarkably different than the Cossacks in shooting skills and target size.
I think this is corruption on a pretty deep level, and I even think it might have been purely 100 percent instigated and caused by LEO, with total lack of regard or concern for innocent bystanders.
OK, I modified it added - - to the modified part:
meeting announced for regular bikers,
outlaws find out & plan to crash the meeting,
cops get wind of outlaws intentions,
-cops set up an armed snare for the outlaws-
things go sideways when the Cossacks and Bandidos start fighting
(fight could have been instigated by an undercover cop)