It seams like you're mixing two issues together. AR10's, assembled with correct parts, are not any more difficult to get running than AR15's. They are not AR15's though, and some of the AR15 rules of thumb do not necessarily hold true for AR10s (gas lengths for example). An AR10 doesn't need a flow through silencer any more, or less, than an AR15. I've shot suppressed AR15s well past 10k rounds without cleaning. AR15's and AR10's with retrofit pistons are a step backwards in terms of reliability, accuracy, and sound signature with silencers. As I mentioned earlier, DI guns are much more forgiving than piston systems.
If you care to look, I posted a link of a SBR AR10 I finished above. It is the actual receiver set and barrel length the OP is asking about. I included some notes about the operating system weight and gas port diameter. The barrel I used was a cut down barrel I had already fired well over 500 rounds through. All rounds were fired suppressed with a traditional silencer. There is no difference in the fouling between the 12.5" length and the 16" length. I used the same silencer in the picture for both lengths. Additionally, I have other LFAR's I have fired many thousands of rounds through. The fouling is not an issue, long or short. Frankly, modern surface treatments make cleaning the BCG effortless.
