Electric is the best way forward for such low useage.

Correct choice of charger OR decent operator training is the key.

I would always point towards the correct type of smart charger then just trusting the operators to charge / equalize charge the batteries correctly.

As for battery filling:

Flip tops & a watering gun are my prefered option, takes slightly longer BUT you know the cells are all filled correctly, ive yet to come across a decent single point watering system.

Not seen the one mentioned above with a white dot yet so I cant comment on that.

Avoid the GNB / Chloride / Exide ( or whatever there actually called this week ) Aquajet system, its total rubbish!