first it is a little bit important to indicate which one. different ones act different, are you talking about the 900?
then most of the AA things will not charge high capacity Ds because they have safe timers for the AAs which limits total charging current or time.
that is solved by recycling it back onto the charger, when your sure it has not yet reached a V-drop.
then the CONNECTION you make could make things go badly, in a range of terminating early (no big deal), or not terminating (bad news), the connections need to be very short and very connected, not bump around or faulter or have higher or changing resitance. so a Holder and short copper wire connection might be better than magnets, just depends on the magnets, are they strong neos, are they plated for excelent electrical conduction?
then the thermal probes, which are practically useless anyways, would not be next to the battery, so the thermal safety would not be in play for the cells.
then termination via a V-drop would need to occur, and the connection differences can slightly effect that, then you have to have enough current going in to get machine visable v-drop (if it is that type) which means you have enough power to blow the cells through the wall
so those are all the things to think about, work SURE you can make anything work.