How is sparring, striking with kickboxing tactics one on one with a couple of half hearted attempts at groin kicks that never land thrown in, relevant to aikido? When you are exchanging blows with your partner at that distance, dancing, circling, backing up, shooting and ground grappling/pounding, how does that take into account the possibility of concealed weapons (his, yours or both) or other attackers. Freestyle training like this is a good idea, it is the specific tactics that you use which are deficient and cause you to come to conclusions which do not fit with my experience.
1) Uke "committing" to an attack alone has nothing to do with an inabiltiy for nage to strike uke. If uke attacks like in your videos he can be hit whether he (A) stalks/ taunts with feints, pot shots from the outside or (B) comes forward aggressively. If he chooses option (B) he just gets hit worse, either method of unskilled attack without knowledge of how to not present any openings for strikes are not designed to be dealt with by an aikido throw but a strike. One exception being when someone is so inexperienced, out of control and uncoordinated that he strikes at you with all of his strength in a telegraphed manner. Moving out of the way alone often will cause him to lose balance or even fall, so will everything else you do with varying degrees of damage to your attacker. If uke doesn't foolishly put all of his strength behind the strike, he can get his balance back and resist nage's aikido technique. Thinking you can gauge if he is using 100% of his strength as opposed to 80% is impractical when hitting him does the job either way.
2) If both participants agree not to strike as in experiment 2, aikido waza where nage remains standing can be performed effortlessly as a counter to any committed grappling attack which attempts to lock and control, throw or take down, however both partners should start at a close distance, almost body to body (where you are too close to strike effectively) and not back away any further at any point during the exercise.
3) Shooting in for a tackle at a striker who stays on the outside, dances and circles, (usually due to a reach advantage) is suicidal as can be observed in the second Liddell v.s. Couture fight. This tactic is effective( one on one, both fighters unarmed) when uke attacks aggressively as in clip 1, as can be seen in the first Liddell v.s. Couture fight.
4) In experiment 3, this will not necessarily encourage uke to attack aggressively with grappling, but to be cautious or just exchange with you toe to toe, the better kickboxer will knock out the other, (after eating a few shots himself the vast majority of the time, even if he lands the first one) should he adopt this kickboxing style of standup as a defensive striking method. Wearing a cup and incorporating groin kicks is a good start, but get some eye protection and open your hands! When you hear your partner's finger nails click against the goggles you are wearing, stop. If you want to train to defend yourself against the average guy, as nage take off your goggles and have uke wear gloves( so he can punch), goggles and a cup.
5) As can be seen in your videos, an aikido throw is not designed to deal with a type of attack which can be diffused by a simple strike as uke can resist the technique at any point forcing nage to resort to a strike anyway, increasing the time needed to dispose of his attacker and decreasing the efficiency of nage's entire defensive strategy. Even if uke does not resist the technique and follows along after his initial "attack" where he is open to be hit as a first defensive response by nage, uke can still be hit even worse due to the vulnerable positions he allows himself to be placed in by "blending" with nage.
I have a problem with the following statement:
"From here, as we can see (inversely) in the video, we should note how many of Aikido's prescribed ukemi responses are actually expected responses mature attackers make in order to not be debilitated by such things as a crude rain of punches and kicks. Additionally, we can say that Aikido's prescribed ukemi responses are actually expected responses mature attackers make as a result of being committed to their victory (i.e. the defeat of the defender) and thus to their attack."
The way aikido is generally taught and practiced, uke is "taught" to attack in manner which makes him easier to hit than most untrained attackers are! As can be seen in clip 4, at least your attacker keeps his hands up as opposed to letting one hand hang dead at his side, he makes an attempt not to telegraph strikes which might actually have some effect if they were to land on a sensitive area (as opposed to an empty handed shomen/yokomen uchi) and balls up in a fetal position in a feeble attempt to shield himself from your blows when he is laying on the ground and you are in a position of dominance. This is still more effective than any attempt to protect yourself once you have been pinned flat on your belly with your face in the mat after not resisting an ikkyo because your instructor could not make the technique work any other way so he tells you "it is the only way for you to learn without injuring you" (when the exact opposite is true) while at the same time he claims that "aikido protects your attacker" (no matter how incompetent he is or what he does). Another one of my favorites is "don't roll away to safety when you feel you are in a vulnerable position and you no longer have any intelligent offensive options available to you, allow me to put you in a positon where I can (1) hit you (2) slam you into the mat face first or with a breakfall instead of getting your arm broken ( both of which you could easily stop/counter ) so that I can practice my pin afterwards"