So how does the mobile kernel work in that scenario ?
Or does that simply not matter, as the unplugging is always intentional and therefore the devices are expected to be getting unplugged/unmounted before hand anyway?
The important thing about the mobile kernel, is that with it, your N7 behaves 100% like it normally does. There are no constraints. In addition, you can charge your device, while using USB slave devices. And you can switch between charge mode and OTG mode semi-automatically, by plugging the OTG adapter. So no need to do anything else or even use the command line interface. And you get USB audio support on top.
But yes, when you pull the power source and your slave devices are not otherwise powered, there will be a small power gap, before the kernel kicks in to supply battery power to the slave. This should pose little to no issue for stateless devices. And even external file systems should get remounted quickly. This works with CM10.1 since they have (re)implemented the feature a few weeks ago. But I think it will not work as a means to power down from a sudden power loss situation, when using the FI kernel.
@b0bd This (sysfs or /proc interface) is exactly what I had in mind, a couple of days ago, when I mentioned a future full ROM variant 'with dual kernel functionality'. I will probably implement this as soon as I have a GUI element to connect to.