Balance aka trim does present itself if all the pax are seated in one compartment, this can be overcome by moving underfloor cargo to different positions to counteract trim positions. Overall weight is limited by the structural max permitted by the manufacturer, but then this can be determined by performance, temperature, TODA etc, too many connotations to go into.
Yes if all the pax carried extra weight, then once all check-in has finished, the weight is calculated to the maximum, then offload status is assigned to first cargo, then mail, then baggage. Offloading continues until all the weights are within specified perf tables and a/c limits.
I think Onan, the whole industry is recalculating notional weights across the board, not just the FAA. As the average adult weight in the 80's was 80kgs, it has risen slightly now. (me at 100kgs)
