Don, I don't agree that nage's effectiveness should depend on uke's performance. I realize that the committed attack paradigm is the party line in aikido right now but it never seemed like a good idea to me. Why wait for a specific quality of movement when you need to take initiative and end the conflict? Wouldn't it be better if we trained to be effective whether the opponent committed, resisted, feinted or tried to run away? In practical application not everyone gives you a nice attack you can work with.
It seems to me, as a complete newb, that you don't really want to study Aikido? The entire (well, practically) system is based upon pure defence, made possible with the force delivered by the attacker (uke).
Now, personally I agree that sometimes the best defence is a solid offence, but that's not Aikido. That's not to say that you can't train for that - by cross-training, that's perfectly possible - but it isn't the Aikido system, right? The very notion that you say you should be effective, when your assailant tries to run away, shows that you don't particularly like the system that Aikido is based on (which would be to never attack, but to efficiently defend).
I would say, instead of trying to change Aikido, take what you can from it, and do cross-training to fill in the blanks of what you feel is lacking.
With everything else - I agree that cross-training is good (in all martial arts), and that some amount of resistance should be put on all parties during training.
I might add that this is why I don't understand how Shodokan / Tomiki competitions work... surely, if all parties practised Aikido as it was designed to be used, each round would be 5 minutes of students standing around starring at each other, waiting for someone silly enough to attack.