GoGo doesn't appear to be updated anymore (at least not recently), but you can manually add them:
GogoMount.lua about line 339:
GOGO_AIR_FAST = {
["Horde"] = {
"item:25477:", "item:25531:", "item:25532:", "item:25533:", -- windriders
"item:32857:", "item:32858:", "item:32859:", "item:32860:", "item:32861:", "item:32862:", -- Netherwing Drakes
"item:32314:", "item:32316:", "item:32317:", "item:32318:", "item:32319:", -- Nether Rays
},
["Alliance"] = {
"item:25473:", "item:25527:", "item:25528:", "item:25529:", -- gryphons
"item:32857:", "item:32858:", "item:32859:", "item:32860:", "item:32861:", "item:32862:", -- Netherwing Drakes
"item:32314:", "item:32316:", "item:32317:", "item:32318:", "item:32319:", -- Nether Rays
},
}
Basically just add in the item IDs for any mounts you want to add. Those are the five Reputation Netherdrakes, I didn't do Armored ones but a few minutes at WoWHead will get you the item IDs in question.
You can accomplish part of what you want with /castrandom, though I really prefer just having one single button to press for flying/ground across all my characters so GoGoMount is still useful to me.
(edit: I put in the Nether Ray IDs as well, since your question was specifically about them as well)