In order to share how I address Aikido training and structuring a curriculum lets look how to define martial arts in general first; else-wise the actual curriculum makes little to no sense.
First, ignore the actual techniques; as they matter little. Just about every style out there strikes, kicks, twists & locks so it's not the appearance of a wrist lock but how and when it's applied.
Second, what sets one MA apart from another should be based in the tokui-waza or rather the first, instinctive, natural, reactive, intuitive, subconscious reaction to an unexpected attack when the defender is under pressure and unable to control the circumstances. This tokui-waza (intuitive response) is based entirely in how you have trained; ergo the old saw about "how you train is how you react (in real circumstances)".
If the intuitive tokui-waza is to directly oppose the attack then your primary MA is one in which the first response is to push back via force directly opposing force; he pushes & you push back, he grabs and jerks & you grab and jerk, he punches and kicks and blocks & you punch and kick and block. This is commonly found in MA such as TKD, boxing/kick boxing, etc.
If the intuitive tokui-waza is to move out of the way of the attack but while doing so grab and attach to the attacker then your primary MA is an avoid/attach response; he punches and you move to avoid but then attach and throw, he grabs and you move to off-balance him while grabbing to throw. This is commonly found in Judo, grappling and BJJ type MA.
If the intuitive tokui-waza is to move out of the way and break the attackers' posture and redirect the energy before attempting a technique then your primary MA is an avoid and redirect response. He punches or kicks, you move, parry, redirect the attacker to off-balance and only then take a waza. This is commonly found in Tai Chi and Aikido.
The way in which your chosen MA applies techniques fits into one of the three categories. Kotegaeshi is kotegaeshi and atemi is atemi but how you enter and apply can differ according to which of the 3 base principles of timing(s), angle(s) and distance(s) judgement & control your MA uses and bases its applications on.
The question often (always) arises and is discussed ad nauseum, "Why does my martial art not include ..... chokes .... foot sweeps .... sacrifice throws ... etc. ...... etc. ....".
The question also arises (again always and again ad nauseum) whose martial art is better.
The "what's left out" and the "whose is better" questions are simply too limited as is the overall understanding of those who pose them. Each of the two questions is predicated on the assumption that any single martial art can include every single technique existent or that any single martial art is better than all others.
In the former, NO MA can possibly include everything and to assume that one can is .......... well you decide how experienced and seasoned in the MA the person making that statement is.
In the case of the latter I personally prefer a Beretta 12 gauge with deer slugs at 50 paces or maybe a nuke. So much of what makes one MA better than another contains so many possible factors; size, strength, pure dumb luck, grease on the floor, surprise, emotional issues,etc., etc., etc. Maybe the best way to describe it can be found in a statement coaches like Tom Landry or Bear Bryant would make ........... "The difference between one pro-football team and the other is the phase of the moon since each has players that are so good that the difference is miniscule".
So ......... the question should be not what was left out nor who is better but what "Core" or most basic principle is your MA based upon.
In Aikido, Tomiki to be precise (as an example since that's what I do), the answer is YES..........Tomiki left out lots of waza ........... and YES ......... Aikido is the best if everything is done absolutely perfectly (which it never is) and if the world turns exactly correctly for us (which is never does) and if the opponent makes mistakes (which we can never count on). Big Deal! Every martial artist alive can make that claim..... so lets drop the issue of who is best (my answer to that is NONE) and focus on the what was left out since that is the real issue and in a sense provides a partial answer to who is better/best. After all, if you are not concerned with who is best then why are you concerned about what was left out in the effort to become better? Why not just accept it the way it is and move on? Wanting to throw foot sweeps or ne-waza into a system that does not contain them strikes me as an effort to improve the system such that it becomes more effective (i.e., "better").
Don't you think?
When you train you want to make use of only one of the tokui-waza principles in order to maximize its' effectiveness so Kano postulated that by using only one primary response and by limiting the number of waza to the least number that both teaches the tokui-waza principle and gives the broadest view of the system you as a player can maximize your reponses and overall ability.
So in the case of Aikido yes, foot sweeps were left out because they do not fit the two arms length/avoid & redirect tokui-waza principle. You have to proactively close ma-ai which violates one of the principles of controlling ma-ai and breaking posture before closing. Then you have to break a second principle which is to continue tai-sabaki and move since entering for a foot sweep requires picking up one foot and momentarily becoming immobile and therefore exposed to the opponents efforts. Violating so many Aikido principles means about 100% chance of failure unless the opponent is doing so many things wrong that the opportunity is just too big miss.
IMHO Tomiki left them out because he viewed the core principle, the tokui-waza principle as more important than mass numbers of waza encompassing everything possible extant in the MA universe. Learn the entire system including all kihon, all kihon bunkai, all kata, all waza, all randori concepts and applications and all embedded principles. Learn them before, I said BEFORE, moving on to things that do not fit that paradigm because to do so means that you are now studying two different tokui-waza principles simultaneously so which one do you make primary?
After learning all the Tomiki ryu and understanding it in the entirety you may look up one day and decide, "You know, I sure would like to see some foot sweeps in my randori because it just seems like they're coming up all the time now."
At that point, once you have learned ALL the system and have TOTALLY embedded the intuitive reactions you can begin to branch out and "add-to" the system and fill in those perceived weaknesses or gaps. And, at that point since your subconscious and intuitive process operate totally from the Aikido paradigm, all you foot sweeps will fit what you are doing and will have a clearly defined Aikido "flavor" to it that will better fit your body type, preferred movements and tokui-waza. Going into foot sweeps or adding things in before you have totally embedded the Aikido paradigm means that the Aikido is still weak and not clearly defined and that the addition of a second tokui-waza principle will begin to cloud and interfere with your primary; your Aikido.
So ....... do I use footsweeps ......... of course.
So ....... do I know/use ne-waza ..... of course.
So ....... do I use waza that are more "classically" within the pervue of Aikijutsu or Judo or jujutsu or whatever ........... of course because I perceive that Aikido indeed has some gaps BUT I think that everything I do MUST have that Aikido "flavor" so as to maintain my tokui-waza principle intact.
I think Tomiki understood. I think Tomiki wanted people to develop their core and then at some point add in the Judo or whatever they perceive is needed whether for efficacy or effectiveness or art or beauty or whatever.
But anything added should contain the "full-flavor" of the paradigm, of the tokui-waza principle.
L.F. Wilkinson Sensei
Aikibudokan, Houston, TX
November (Turkey Day) 2009