Heya,
I find that Officer training takes way, way too long to be useful, especially since after mid-game rolls around and with the infiltration system, no sooner are my soldiers back on rotation than I need to send them to another mission. Higher-level officers inevitably end up being the soldiers on the highest demand, since they are required in missions that take a long time to infiltrate. This has resulted in my being in late October without more than a couple of higher-level officers, which I can't ever put in the training room again, because training takes 10 days and I will need them in the meantime for very intense missions, like regional HQ assaults.
My simple request is: How do I make Officer training in the style of Psi-Lab training? That is, the officer in question is selectable for a mission while training, with the effect that their slot is taken up during the time they are infiltrating, but also meaning that they don't lose progress already recorded and having to start from scratch when they get back on the Avenger. Which both makes sense - what, do they suddenly forget all they learned during training if they go on a mission - and it's a fair compromise, as far as I'm concerned.