I think you need to be careful what you wish for, Eloethan.
Abolishing First Class wouldn't necessarily increase the numbers of passengers using the trains, and could even reduce them if first class passengers chose to fly instead, so if the train companies lose revenue by not providing First class accommodation, they will have to increase the fares in standard class to make up the deficit.
As for empty carriages, and overcrowding, it's up to the train companies to manage their rolling stock effectively.
I was once travelling back to Newcastle from Harrogate and for some reason, I think it was at the time that all planes were unable to fly because of the volcanic ash cloud, the train from York was horrendously overcrowded and the guards let people with standard tickets use first class, so they do have discretion.
What annoys me about train pricing is this business of if you want a return ticket from A to C via B, it is sometimes a lot cheaper to get two single tickets, or even buy separate tickets from A to B and from B to C, but you only find that out after three quarters of an hour's headache-inducing searching on the Internet. That really shouldn't be necessary, the most cost effective way of making the journey should be clear and obvious.