Before doing anything "seismic" I would systematically check out what current drains there are on the battery. so better understand the cause(s) of any issues.
This can be done using a multi meter but typically more easily with a unique current tester
LIKE THIS, if blade fuses are used in the various fused circuits. You simply put the inspected circuit's fuse into this unit and plug the probe back in. My van also used a blade fuse in the main battery feed, so I could check the charger itself.
This can be quite revealing.
In my case I found a fundamental error had been made in wiring up the radio; here an automotive radio was fitted, but its twin supplies were taken from a single feed with nothing replicating the switched "ignition", resulting in a significant unnecessary drain.
You might also find the charger/controller itself inflicts a real parasitic drain. Here I have found on a friend's van the solar controller he had fitted had a very high self drain, overnight sapping all he gained during the day!
Armed with knowing where the issue or issues are, helps in finding solutions.