I was wondering if using a frequency in the kHz range would be a good idea because of how far the radio waves can travel… or would the frequency end up too crowded?
Or maybe even a channel dedicated to talking over long range (emergency, government announcements, etc.)
It’s a nice idea but a “Longwave” frequency would need a bigger antenna and that’s just the beginning of the engineering issues. Amateur radio operators and government agencies are all over the spectrum and already doing this kind of thing. The equipment can get a little pricey.
You kind of describe Shortwave radio here.
When I added that, I was thinking about LowFER (to be specific the 160-190 kHz range)
You are right though, you would need a much larger antenna (… I forgot about that …) 
1.8 kilometer wavelength? 
For a small, portable unit like the Gotenna, the antenna must be of a manageable size. If a frequency range around 160kHz was used, the antenna would (as pointed out) need to be HUGE to be optimal. If a smaller antenna was used to keep size in check, the effectiveness of the device would be greatly compromised. Probably to the point that the range that you would get would be less (possibly MUCH less) than that of a UHF device like the Mesh (despite the disadvantages of UHF vs longwave for long range communication).
We all could just drag a long wire antenna behind us 
It would help with propagation on the ground.
I actually signed up a while back to use the new amateur allocations 472-479 kHz (630 meters) and 135.7-137.8 kHz (2,200 meters). It required us to register out operating QTH ahead of time. I have not received an rejection letter so I should be ok to operate there even though I haven’t done so yet.
lol roughly 260 Feet of wire! (Di-pole)
http://www.westmountainradio.com/antenna_calculator.php
I always get a giggle when I hear people asking about why they don’t make hand held HF radios that you can carry around. People do it (Man Pack setups) with “coiling up” the antenna but between frequency and proper height above the ground they pretty much are poor performers. They do drag a wire behind them, http://www.hfpack.com/
One of the coolest long wire antennas I’m aware of is for US “Doomsday” jets that have 5 mile long antennas they can deploy in air. I think those are for talking to our nuclear subs in the ULF band.