extra

1) power
2) radio
3) antenna

did I mention power.

If you are doing emcomms things are bad enough that you can't count on anymore power than you can carry. I would think you should bring enough battery to operate full power for three days and recieve constant for ten. Then double that because you know Murphy will attack.

Then consider alternative power such as
1) a decent way to hook up to whatever vehicle might still have gas - this includes inverter, conditioner and jumper cables.
2) a decent solar alternative - after the storm passes there still may be need for H & W messages and the phones may take a while to restore
3) If you carry QRP type equipment you might be able to use the power source in a BayGen type radio if you are into some home-brew.
4) Plastic tarps to cover your station incase of leaky roofs. Simple trash bags are better than nothing. Wet radios don't work.

Presuming that you will transmitting from strong station such as mobile 2 or 6 meter unit or a fixed station at a shelter etc. Whatever you main radio is you should consider alternative / back up radios:
1) Carry a good tri-band HT
2) CW QRP HF.
3) Cell phone - Who says every message must be delivered via Radio?

If your main station goes FUBAR the HT should be enough to get you back on the net to announce the condition of your station. If Both your main station and your HT go FUBAR or the Net goes FUBAR then your CW-QRP-HF rig will allow you to continue usefully contacting out of the disaster zone. Something like the ROK-MITE with a random-long-wire antenna wound around the box can be tucked into the same space as a PSK and might even weigh less. Works on very little power which could be rigged easily from any of the above alternatives.

You should have antenna intended for use on all of your stations attached or stored with them then you might also add

1) antenna tuner and SWR meter so that you could borrow antenna from whatever is around

2) Largish spool of wire and another of twine. Random-long-wire antenna are decent for any freq if you can impedance match them - See #1.

Of course you will also want the standard survival stuff but in the eventuality that you end up in a shelter or other fixed / loud / busy location you will want to also carry comfort items such as

1) ear-plugs and eyeshades. Who knows when you will be alloted sleep time. You must be prepared to invent quiet and dark to enable good sleep.

2) Power-bars, GORP, Ramen Noodles, MRE. - Maybe you will get three hots - maybe you won't. They will still expect you to continue communicating anyway.

3) Water and water purification and water carry.

4) A good tent would be helpful as well depending upon deployment.

Just a few thoughts.