I think you would at least need people that you trust in order to:
A) show you these skills
B) be honest enough to tell you wether or not you are progressing or doing the exercises correctly. Otherwise its easy to get self deluded.
C) When you initially start you need someone else pushing on you so that you can feel the difference between proper and improper movement. Perhaps once you have some understanding of this, you can do tons of solo training because you can recognize the feel on your own.
D) If you have a group of somekind, you are more likely to stick with the training and will likely make better progress since you can bounce ideas off one another. Sure if you are hardcore enough you don't need peer pressure.
At the end of the day maybe you don't need friendship (its not going to hurt), but it does help to surround yourself with commited people who are interested in these skills if for any other reason than having a variety of body types and skill levels to play with.
If I may, while all that is true, you still only outlined learning some basic connections through push testing....er...okay.
Solo training is key...absolutely essential,, paired testing as well. However, legendary, IP/aiki is never, was never, a completed skill learned by remaining in these sorts of environments. It's kind of like being retarded in it's true definition of being developmentally challenged, people who remain there will never fully develop, and can and will be outmatched by those who've taken it literally, to the next level.
Contrary, to some of the myth making seen here, there are more and more stories coming back with real experts in the ICMA who have had trouble in dealing with western wrestlers and MMA'ers at seminars. Now imagine the same westerners with IP/aiki and with those same years of experience in fighting skill.
More and more are thinking this way. I think it's a good thing.
As I said though, for those really searching for total development, there are those who attempt to cheapen those efforts. Something any serious martial artists should look out for..