So you suggest simply introduce a techniques from judo to fill up, what you perceive as a gaps in aikido pins? We all know that O sensei was well aware about judo repertoire of techniques having some visits in Kodokan. Being a Budo genius, he would also clearly perceive gaps in aikido pins. How come he didn't introduce more efficient pinning techniques from judo to replace those deficient from Daito ryu?
May be ultimate efficiency of aikido pins was not his main goal?
I guess the Aikido moves were developed to actually break the arm not hold someone down. In combat on the battlefield you would have no reason to try and hold someone or you would be killed by someone else. Like I said the Aikido pins are probably effective on most people, but they probably will not hold an experienced grappler for very long.