I would agree the easiest thing to do is replace with AGM batteries. It appears you leave the van unattended for long periods of time. Are you relying just on solar to keep the batteries charged during that time? 100 amps could be a little low to accomplish that, you would have to check that you are not getting behind the curve. You could also plug in and allow the shore power to keep the battery in float.
If you can't plug in and not sure that you can rely on solar the best practice id to get home from your trip. Then make sure that you bring the battery to a full charge, this means you will need to see it go from bulk, to absorption, to float. At that point you would turn off everything or pull fuse or battery disconnect.
If moving to a Battleborn you have a couple of choices, remove Separator/ACR and go with a DC to DC charger, or you could go with Li-BIM 225
to replace the ACR. There are a few variables in picking the DC to DC, a lot depends on available alternator power. Most DC to DC are referenced by output power, so if it a 30 amp output, it could be 45 amp or higher on input. When choosing it is good, to pick one that has some flexibility in programing output. It should be noted that Sterling DC to DC actually states their sizes on input, so sterling 60 amp may put out 45 amps.
Blue Sea ACR 762X
Blue Sea ACR 7610 or 7611