^ Personally, I don't really need a safety track. I am a pretty good judge of where to set my levels and 24-bit allows you to be pretty conservative. I would love a stereo version of this recorder, though, with its variable plug-in power. An 1/8" locking male to two microdot female Y-cable and a pair of 4060s with that would be awesome...
If you're using this a bodypack recorder (and it looks like it would blow past any competition! Superior to the Tascam, and priced way way waaaaay under the Zaxcom / Lectrosonics products. Although... the new Deity TRX would now be tough competition for it!) then having a safety track mode would be
fantastic.
If that 1/8" stereo input could handle line level so you could use an external preamp or phantom box for full-size mics, it really would be a Lectro SPDR killer, as someone else mentioned.
Regarding safety tracks:
<snip>
In other words, there is zero reason I can see to have something like the Track E record in anything but 32-bit FP.
Line level would indeed be a FANTASTIC option, perfect as a mini back up recorder I can feed a mix from my main recorder, light enough to even use for run&gun bag days.
However, is something else than 32bit needed?
ABSOLUTELY! Too many productions have and expect a 24bit workflow. You can try fighting that if you wish at your own peril, but you likely have better battles to pitch your tent at, especially if you're just a day player. Is why I'd take a 24 bit "safety track" approach over 32bits in most scenarios for myself.