Another charging option I haven't seen mentioned on the forum is using both pack and bank charging together. I know sounds crazy at first but stick with me. Most bikes have a pack charger already. Most pack chargers voltages can be adjusted internally as well. The idea here is to turn down the voltage on the pack charger to the float level for the pack. Then by adding some small 2amp or less (for small physical size and low cost) soniel chargers (1 for each battery) you have your bank charging advantages.
Charge profile looks like this:
Initiate charge and you have bank charger plus pack charger max amperage as your charging amperage. As the voltage increases the pack charger pushes less and less as it is set to float voltage. Once the pack passes float voltage the only charging amperage is coming from the bank charging chargers. The soniels are small and reliable (fairly easy to find room onboard for them) have a nice charge profile. The soniels do a nice gentle finish charge on each individual battery. Charge times generally work out the same as the pack charger alone before it was turned down. Wiring and mounting is simple. Charging is plug and play since all the chargers AC feed can come from one source. Nothing to change or reconfigure for each charge cycle, just plug one cord into the wall and the rest is automatic and also onboard for opportunity charging. The pack charger can't overcharge or undercharge any batteries because the soniels take it out of play automatically once the pack voltage rises past where it is set.
One other side benefit is partially avoiding the biggest drawback to bank charging. The case where one bank charger has failed to charge and you take off with 4 full batteries and one dead one. Dead one (permanently) becomes the operative word for that battery in this situation very quickly. With pack plus bank charging at least the battery served by the failed bank charger unit is about 80% charged by the pack charger.