Good points. I'm certainly interested in hearing from more of the current 250 and 300 riders. If the 250s are truly at a performance disadvantage compared to any of the 300s, it would be a shame to combine the classes and penalize the 250 riders.
The main impetus for combining classes (with comparable machinery) is to fill grids. If this cannot be achieved, because the only comparable bikes share the same displacement, this wouldn't work for obvious reasons. Sounds like we need to discuss more at the rule change meeting...