You don't need internal power for spontaneous technique. There is no "A implies B" relationship there. I don't think the two have anything to do with each other at all, though there is plenty of room to quibble.
I tend to think if you want to develop Takemusu Aiki, the long and arduous quest for internal power will set your timeframe back a lot, particularly the intent-driven way you guys advocate training. After years of being in your heads you are somehow supposed to let it all flow? Good luck.
You don't seem to have a very good understanding of what kata training is and what it is supposed to give you. It also doesn't sound like you had very good Daito ryu training.
I think Takeda was very much a showman and when he was on the road teaching Daito ryu he was in part, selling amazement, wonder, and mystery to the bulk of his students. So it may well be that the syllabus of Daito ryu is inflated.
But I don't think his career would have lasted long if he was teaching an empty vessel. Regardless of whether there was a simple secret that he taught only his closest students and cautioned them to never show them in public because they were so easy to pick up on (though I think this only comes out of accounts from Sagawa and Horikawa?) if the hundreds of other kata were not useful for getting to these principals, then word would get out and people wouldn't sign up for 10-day seminars with the guy.
A kata, particularly a koryu jujutsu kata, is a training tool. It is designed to instill techniques and principals. I think you could actually term them habits, and they are ABSOLUTELY what you want to have in a combat situation. A kata may or may not be applicable to a common situation, or even a real situation, depends on the system. But it will set up open-ended systems of response in the nervous system and the practitioner will react in a way that is intended by the system's founder and instructors.
A well-designed kata delivers feedback as it is executed - if your posture is incorrect the throw will not work, if you use too much muscle uke will land over there instead of right here - but you cannot begin to know what is going on without an experienced instructor who can correct your form, and/or an experienced sempai who will stand there and not move unless you do the right thing.
I have lately been using the term "external" and "internal" in terms of training methodology - an internal system would be one that uses imaging and a mental process to find the proper form and build skill, whereas an external system relies on the instructor teaching and reinforcing an external form, which the practitioner internalizes and builds skill from there.
Either way, what you DO in a live situation is act spontaneously. Whether you like it or not. No one who has ever written on the subject of combat skills or self defense tactics has ever had much positive to say about how useful the conscious mind is in a life or death situation.
You did some Aiki training (no offense but it sounds like either you weren't into it or it wasn't very good), you did some free training. You were able to react spontaneously in the free training, and you responded with Aiki. I'll take your word for that because I don't think Aiki is something that "powers" anything. Regardless, this is no reason to believe that you were able to respond spontaneously because of your aiki training.
I think there are some interesting comments in here:
1. I think the state of aikido specifically refutes the A then B relationship. There are undoubtedly people practicing aikido with no internal power or even a desire to learn about internal strength. I think the argument is a qualitative assessment of the proficiency expressed by the individual practitioners.
2. I think internal power training inherently applies a greater burden of training. You can see that as either pushing back the timeline of training, or increasing the training regime. I think in either case it is fair to expect the commitment to achieve that level of proficiency is extra-ordinary. Again, not everyone will want to undertake that path. I think the issue is that aiki was not previously thought a tangible achievement; rather, it was considered a intangible expression if you stayed the course long enough.
3. Kata in aikido is damaged. The roles of uke and nage have taken on undesirable properties which [negatively] affect the relationship within kata. I think we need to work on our kata to return to a state of logical and impassioned interaction with clearly communicated feedback for both roles.
I still waffle on the role of habit in stress environments. One of my military friends spoke about an issue in basic training surrounding the trainees habitually removing their headgear following a movement exercise. The issue was that the trainees became used to removing their gear following a long run. For every story I hear like this, I will hear another about the importance of automation.
I think the idea of stability with internal training is designed to create a natural state of being on which you can base your action. When I played athletics, this natural state was coached under the "athletic position" - a state of potential energy to be focused in action.