these beings have gone on in the re-read, skipping around a bit because story in that book is too familiar after watching the HBO show roughly 1.5 times.

There was one interesting difference from the show to the book concerning Jon snow and Samwell tarly and their advancement to black brothers. In the show, both were immediately and inexplicably advanced, whereas in the book, samwell was originally not advanced until after Jon showed his wisdom to the maester. This wisdom shows why Jon was chosen as Mormont's heir.

The wall is the single most important structure in the realm, it is clearly ignored often, generally to the despair of all when the walkers come. The citadel of the Maesters is known to send out the white ravens upon the turn towards winter. Why does not the wall have white ravens or such messengers? They should technically have had a set of special messenger birds, both to send to Winterfell and to send to the citadel for further spread of warning upon the tripled call of the horns.
Is it because they come so rarely that the system is missing, or is it because it was abandoned over the eight thousand and something years since they last came?

To think.. you put the Wall (Others-area) and the Citadel lumped together in one paragraph. We, as readers, know the Citadel is up to something... and we also know they are decidedly anti-Dragon (we learn in AFFC the Maesters have sent someone to kill Dany & her Dragons). I won't dig too far in to THAT juicy information, though. Instead, I'll leave a link here taking you to an essay on it and other interesting bits of theory from Feast for Crows and you can work that out yourself. [tiny note]: At the top of the page you must choose your threshold of "books read" in order to see any information.

In regards to the Wall....

The men of the Night's Watch had long-since forgotten what the true purpose of the Wall actually is....... to protect the Realms of MEN against the Darkness (the Others). For 8,000 years they've manned this Wall, not attacked by anything, to the point the whole Others thing became legend.. scary stories to go along with Grumpkins and Snarks. It seems only Samwell, Jon & Maester Aemon have taken the whole thing seriously, which baffles me based on what all the other brothers saw @ the Fist of the First Men. (How could they not 'get it' now?)

There are bits and pieces of lore concerning the Wall scattered throughout the series and the most interesting, in my opinion, is the fact the Wall is not only a physical barrier, but a magical one too. What is the magic keeping the Wall standing? The Oath of the NW Brothers. We learn some of that from Coldhands in ASOS and some from Maester Aemon in AFFC. So what happens now that the LC is "dead" and the majority of the NW Brothers have turned on their LC? Is the magic of the Oath gone? Will the Wall fall? I believe it's what walls in tales do, yes?

Another thing of interest to me is that the Oath, itself, tells the Black Brothers to guard against All Realms of Men, but for some reason they don't believe this includes the Wildlings.

Either way, the NW does have a pretty large rookery that Maester Aemon kept in order to send word to as many holdings in the North as possible. I'm sure one of those was trained to make it's way back to the Citadel, too. Or at least the word could spread from the North, downward. But to be honest, I don't think very many brothers thought it necessary. Right? What's out there other than Wildlings and Snarks and Grumpkins, after all.

These beings have seen just that connection between wall and citadel, Valarya. It would not be surprising if the Maesters have been tasked specifically with eroding support for the wall. Nor would it be surprising if Maesters over the years assigned to the wall, have been tasked with derailing the watch into caring more about the wildlings than the real threats.

It is clear that the Lannisters to a large degree care not about the wall. Same is probably true in many other families. At the same time, it is clear that the Targaryens did care about the wall, no doubt because they somewhere in their family history knew somewhat of what the wall is all about. This history was probably lost in the rebellion.

These beings have noticed only two of the great families that clearly have not forgotten the purpose of the wall. The Targaryens and the Starks. Targaryens through their supposedly draconic blood and loyalty to dragonkind and the Starks to their intimate connection with the wall.
One of the problems with the wall as a long-time system is that any system utilizing celibacy tends to breed away loyalty. People might stay more loyal and focused at the moment, but over the generations, it will mean a loss of people. You see the same in religions where the priests are required to be celibate. Those with strongest faith, typically those that become priests, are denied reproduction, which means that the strains of greatest faith are snipped off.
If there had been no Starks in Winterfell, then it is possible that the wall by the time of the books would not have been undermanned, but instead unmanned.

These beings have a theory on the further books...
If Daenarys does eventually land with her entire army in Westeros and it is not crushed, then might not the unsullied be the perfect crew to strengthen the wall in the region of numbers? They might not be very individualistic or have any strong leaders, but others could supply that. They would be strength of numbers, whereas the regular watch would be the officers.

Another problem with the watch is that it has over the years become a dumping ground for those that are unwanted, be they murderers, poachers, rapists or otherwise. (another influence of the citadel?)
While this certainly gives some strength, it makes the wall a place almost none wish to go.

One of the reasons used for the celibacy, to avoid a king of the wall popping up and taking up fight against part of the realm is logical, yet still flawed. Wall-kings have still popped up. Instead they should have allowed families, but had strict rules against hereditary roles beyond "steward, ranger, builder, ...". A set of multiple commanders, say three working in a committee, would also have limited the issue of wall-kings. There should also have been a regular tax of the entire realm to supply the wall with materials, be they food, weapons or men.

These beings have a theory on the wildlings as well. Might it be that the first wildlings intentionally went north of the wall when it was built to keep the watch in constant fighting trim and awareness?

Post done. Feel free to rip into it like a freshly caught, tender and juicy riverpig. Use those large teeth.