I just finished rigging all my electronics on my cc and am thinking I should probably buy an onboard charger for battery maintaince. I have a my starting battery with essential electronics such as fuel pump, nav lights, and bilge. I have all my nonessential elect. Such as radio, interior lights, light bar, chart plotter on a dedicated battery that must be manually maintained, then I have a 24v trolling motor which obviously uses 2 batteries itself.
Keeping weight and space in mind is there any way I can wire my 4 batteries in sequence simply to charge of of 1 on board charger or will I need to do the obvious and use on charger on the 24v system and another on the 2 12 volts?

You just need a 4 bank charger.