I am not aware of any off the shelf solutions for making the battery pack easier or faster to swap out. For a custom solution the first thing that comes to mind would be to make a rear cover out of aluminum that has a hinged lid on top that the battery pack could be taken out from, and a new battery pack put into, for a fast swap. Or maybe a lid could be cut out of the original plastic cover, I am not sure if it is strong enough to handle cutting anything out of it though.
A battery charger with a higher output Amp rating could be used to charge the battery pack faster. For example a 24V 3A charger would charge the battery pack twice as fast as the original 24V 1.5A charger. The only downside to this is that charging the battery pack faster also lowers it lifespan. It will not lower the batteries lifespan too much though, and is a good solution if you want to use the go kart more than one time per day.