The M4 mag holders are worth a shot. Maybe some sort of foam "liner" like above can keep them from rattling around on the run? Even when it I'm not carrying it as a secondary, I personally find the holster handy because we often play in rough terrain, and having my hands free helps a lot sometimes.
As for the 12gram lanyard, here is a close up:
I had a buddy drill and tap the end of the plug with an 8/32 x 1/2" hole. Then I used an 8/32 x 3/4" RH machine screw, with some nuts and washers to provide space for the nylon cable clamp to spin freely.
Next, I removed the weaver rail from the underside of the barrel, and used the original screw to attach another cable clamp. For the lanyard, I stole a hair scungie elastic loop from my wife. (thanks, sweetie!
)That, with a knot in the middle, helps to prevent snags, and is easy to replace if it breaks. Having it on a lanyard is a HUGE help because I was constantly dropping the dadgum thing in the leaves when changing the 12gr.
My last little tweak I use sometimes is a Trinity Recon barrel:
Ariakon uses Spider threads, IIRC, and I snagged this cool barrel used. teckpeebee talked about them a while back, although they are no longer made. The end is an aluminum "rain cover" that unscrews to reveal the porting underneath. The ported gases are directed back toward the shooter, making it noticably quieter, especially with a 12gr gas source. Its hardly a suppressor, but it helps a little bit and also adds a certain something.
Hope this helps. Update us on how the M4 mag approach works if you think of it.