just my 2 bits.
Although it would only go down to a 12 cell or 2 sub-pack level... I would think it would be much easier for connecting and disconnecting to only attach to the plastic piece side and just leave the circuit side alone.... but single sub-packs level is nice, it just needs both sides to come off to connect.
Even at a ~5 Amps rate it would take over ~20 Hours just to charge the pack up once discharged... If you are going to spend ~20 Hours is would be much less complicated to just charge the whole 120 cell pack at once with one of the ~180V ~300mA trickle charge methods people are using.
For discharging it would still be useful to narrow down to one or two sub-packs at a time... if you do 1/2 the subpacks at one time skipping every other one in the series chain ... to avoid discharging interaction ... and then the other 1/2 second... you should be able to discharge the pack much faster , and just as safe... it would cost more... you would need multiple smart NiMH battery pack discharge units... if you are doing the 12 cell - 2 sub-pack option you would need 5 Discharge units... and if doing the 6 cell - 1 sub-pack option you would need 10 discharge units...
If the discharge units you pick happen to also be smart multi-cell battery pack charge units as well than you can skip the HV ~300mA charge and just use the same 1/2 then 1/2 method for both charging and discharging.
I would suspect that the relay option with just one smart charger / discharger would be a less expensive way to automate the process ... but it will take much longer .... but it is all automated so I guess the time factor matters far less.
this was my ramble.
