Interesting Akironin that you should bring this up. Personally I believe the MCMAP system and the Systema/Battle Sambo systems are good real world hand to hand combat training.
Compared to the old LINE system which I've had some exposure to I do like the MACP system I just think a few tweaks could make it more effective.
Interesting that you bring up Systema, it started to become somewhat popular in Aikido circles awhile back due to Stan Pranin and the Aiki Expos, and being a DT guy and interested in "real world" applications, I picked up some DVD's and was totally not impressed. In fact I became some what cynical on it. Also picked up some "combat Sambo" and was interested in what they had to offer.
I see Systema as hard sell for DT instructors in Military/LEO work, but Sambo as an easier sell. Those two target audiences don't really have the time in their training schedules to devote to H2H, in the military it makes some sense, as weapons based systems are tantamount to their mission. In Law enforcement it makes NO SENSE whatsoever as hands on a suspect is such a commonplace circumstance it begs the question as to why not? But again Police Departments have X hours of inservice a year, and take away those hours for Cultural diversity, Cultural Awareness, Sensitivity training, Sexual Harrasment, Hugging puppies training, and so on and so on, they may be lucky to get 4-8 hours a year. So styles like Systema, Sambo, Aikido, BJJ or whatever need to be pared down to gross motor skill movements, retainable and able to be performed in full gear.
Again, is MCMAP and Army Combatives the end all be all, by no means, but it is a step towards codifying a system that can as you say be tweaked and revisited based upon Soldier/Marine feedback from the field.