There's a lot of usecases where it may suffice to keep WLAN connectivity, which usually should work, esp if you haven't switched 10mW->100mW in connections advanced setup.
For GPRS/3G data it depends where you are (how far from base tower) and what the modem is doing. It may work with modem on, as long as there's no cell handover and you are close to the base station tower so the TX power the modem needs to use is low.
Checking the air network situation by querying modem about some service parameters - which Konttori 'promised' we get access to, eventually - might help in deciding if we may dare to keep modem on. Reducing risk and impact to system (e.g. by sync, stop certain processes, umount), might be another way to cope with occasional case *when* modem actually hardkills the power. If it fails one out of 100, and no filesystem damage - where would be the limit you'd be willing to accept?


The idea of a script managing all the things like making sure there's a charger and device actually switched to charge mode, to handle all the power hog kicking, and also do things like mentioned above for modem - this will for sure increase safety of the whole procedure. But only if the script is correctly working and tested. For now it's much safer and gives better feedback for developing such script, when users try the manual method and report here about success and particularly about problems they had. That's the reason why I hadn't included method-2 straight from beginning.
For the 'in the field change' I promised I'll get something for you. It obviously will need some hackerish DIY hardware (maybe I'll produce a small bunch of those dongles), and it will need a *script*, so see above... ;-D


See above for rationale about modem keep active during battery hotswap. Also I doubt modem will play nice with SIM changed while powered up. For swapping SIM on a deactivated modem - while rest of system stays on - I see no particular reason why it shouldn't work. Except maybe from cellmo drivers etc *main system* software not capable of dealing with that. This will give nice errors then :-P


cheers
jOERG