You could also take a note from actual militaries and give people two ranks during training, where you can then find out if people are capable of tying their own shoes. Then everyone can start off at, say, subcommander, and it would be just fine.
We don't have any real required training though, we throw even the most green rookies feet first into the fray. Would help tremendously for weeding out the unstable elements, but probably not a good idea, still just a game after all.
On the overall structure: I'd avoid having a rank of 'squad leader'. It's more of a position on a mission, and mixing up the two can result in confusion, so it's better to avoid it.
Why no squad leaders? In practice it's often the same people being appointed squad leader anyways, and on other (less structured) missions it's often the same people being regarded as the natural leader people will listen to. This would make that official, and avoid people that have no real leading skill or ambitions but who've survived for some time to have leadership thrusted upon them.
Also, I don't quite understand it. Specialist/Subcommander people - are we talking of Simus here (let's take her as a benchmark)? Or Adepts in Piecewise's structure? I'm confused again, I'm afraid.
Simus as well, yes. Mostly people that aren't generals, but with more responsibilities than a squad leader. So if, say, Milno appoints an official second-in-command, that person would be at the 'subcommander' level.
Then it means that Piecewise's scheme was right, after all, with three lower non-commanding ranks. The first two exactly could be 'novice' and 'proven novice' as you want, and the third would be that 'more skilled, not commanding'.
Hmmm. Overall, somewhat amended Piecewise's systems seems the best answer to most of peoples wishes and needs. I'll try and post my take on the system later today.
My idea was for 2 non-commanding levels, but three could work I guess (with the third being the highest sans leadership responsibilities). Could be handy for vets who are clearly better than the regular 'proven trooper' but who don't want/aren't suited for commanding. They wouldn't have position authority, only whatever personal authority people give them (right now, outside of generals, personal authority is what we go by).
For roles, I'd really keep that fully apart from ranks. If sniper A is much better and experienced than sniper B, but they have the same rank, then A won't have official authority, but B might still listen to him due to A's personal authority and greater knowledge.
Also, if we do this, then I'd say everybody (apart from generals and sub-commanders) start at the second rank (proven). Mostly so that everyone has an equal chance. People who are competent will distinguish themselves soon enough.