Right now in Arma 3, you can easily grab what ever you want, and do a mission. It's so easy, almost too easy. Now, of course, the simplicity matters, more so for new players who don't know how to play the game. But it shouldn't be that hard. I know games thousands of times harder.
Anyhow, it should be worth the time to create a logistics system for Arma 3. It should be simple, but none the less, require supplies and such in order to do missions. This would create a stronger connection between infantry and vehicles, and provide a much needed "lift" to the whole "Combined Arms" title.
Sling loading was a great addition, but it doesn't quite cut it. It's not used as much as it should be. Part of this is a result of mission designs, and popular demand for a "straight in the action" scenario. It's fun, but those kind of scenario's become boring. A way to have logistics thrown in to the mix would spice things up while still being fun.