However the techniques of Aikido (shihonage, jujinage, Sankyo etc. etc.) cannot readily be adapted to unarmed fighting. In fact it would be really silly to try. The whole of Aikido's technical syllabus is simply not an effective means of unarmed fighting.
What training, testing, experience, professional credentials etc. do you bring to the table to make such categorical statements? The quoted post above is totally the opposite of proven, repeated results using Aikido waza and tactics in actual situations. From my own testing and experiences (and those of people much more skilled in Aikido than I) Aikido gives good options for dealing with certain weapon attacks and can work quite well when one is armed (weapon retention) also, but the possibilities for success are exponentially increased when one deals with an unarmed attacker. The measures applied are almost identical if the Aikidoka is armed or not, there is no need for high variation between the armed and unarmed approach unless your armed waza is insufficient to start with. The weapon retention aspects are directly related to the unarmed tactical paradigm.
Many of the safety measures one takes in properly dealing with a blade for example are not required with an unarmed attacker, providing quite a lot more opportunities for effective waza and tactical creativity and adaptation.
From your posts above I honestly get the impression that you are thinking of using Aikido in a "fight" (i.e. trading of strikes/blows, grappling for a superior position etc.) with an unarmed person. If you are doing this then you are not doing Aikido and not adhering to its tactical paradigm. Of course it would not work if you approach it this way, have you ever seen a Kendoka or Kenjutsuka aim to trade strikes (block and counter) with their opponent? No, one moves in to take instant victory, engaging their strategy and path to domination long before physical contact is made. This is Aikido's ideal domain and the concept works well both when armed or unarmed if one understands how Aikido works in a tactical situation.
I'm not sure what level or type of Aikido you have been exposed to but having trained with Shihan in 2 different Aikido styles who both view (and have literally used) their tegatana/shuto (hand blade) as if it were a bokken, quite often I don't see how one cannot apply the basic principles of the striking/thrusting blade to unarmed tactics via good use of tegatana. What you are saying does not hold up to actual testing imho. the difference between the use of tegatana and actual katana are minimal and operate using identical mind and body concepts.
So unless I am missing something Chris you need to explain why you believe the techniques of Aikido cannot readily be adapted to unarmed fighting. What objective testing and research has led you to this belief? This of course given that the vast majority of Aikidoka do not train the art with a true self protection mindset.
But it also has techniques to deal with:
Them armed, you unarmed.
This is a good concept but has great practical limitations regardless of what real unarmed skill you may have when facing a weapon. Have you ever put on Bogu and tried to disarm a semi-skilled Kendoka really trying to hit you? You should try it sometime if you get the opportunity, it puts the "bokken disarm" concept in a whole new light.