Not much of a story really is it ?
More trains = more cost = higher fares so people won't like that.
Most of the seats on the train are fine, and as has been said, its just the 3 seat bench thats a problem and thats only a problem for a few trains a day during rush hour when used at capacity.
I use the Portsmouth fast trains to an intermediate stop and out of rush hours its always two thirds empty. Even in rush hour, the person on the end has one 'cheek' half in the gangway, but so what ? Its not for hours and half the folks like me get off partway and people shuffle around.
If they MUST work on the train in rush hour, thats what First Class is for.
Or they and the rest of the passengers can lose some weight/width as 'normal' size people certainly can fit in as long as there is no expectations of being able to wave arms around etc.