Is inefficient and dumb, there's a reason why no country in the whole world use this system. You want competent officers that know what they do, not the ones who knows how to run in a popularity contest. Because that's it what this system going to turn into IMO.
To be clear, election isn't necessary. In wartime, most promotions will be handed down from above due to that being more efficient. What this does is encourage the troops to make their opinion known. Senior officers can simply say "no". And yes, the system will be refined over the decades.
In a way, it's a military version of syndicalism - which, if you haven't guessed from the fact that I'm writing an IWW-wank, is an ideology I favor. Veteran soldiers won't be voting for someone who's just a people pleaser. They'll want someone they think can
command. And just as workers in a factory will probably have a good idea of what it takes to run a factory, soldiers will have a good idea of what it takes to be an officer. They won't have the whole picture, which is why the final decision remains in the hands of the higher-ups.
At times, there will be issues. Some officers will get promoted purely based on their popularity. But I don't see much difference between that and someone getting promoted purely based on them being an ass-kisser. If anything, at least the popular guy has the confidence of the troops.
I don't plan on this actually having a noticeable impact on military operations, by the way. The main impact for the story is that a higher proportion of ASU politicians will be veteran officers, having developed their political skills by running for promotions.