I think your presentation of the 24XX rules is one of the best out there. Specifically, your language about when a roll is triggered is very precise which is helpful. (This also helped me understand the new framing of the "Threat Roll" that John Harper laid out in his new Deep Cuts supplement for Blades in the Dark.)
But I was left wondering if I've been misunderstanding about 24XX generally or if you're doing something slightly differently with 24BLUE. In the DICE section you mention:
"A standard roll uses a d6. Max size is d12.
• Skills can increase the die size up to 3 times.
• Traits can increase the die size 1 time.
• If helped by circumstances, roll an extra d6.
• Only 1 skill, 1 trait and 1 help can affect a roll."
My understanding of 24XX more generally is that you use the highest die amongst any skills that are relevant and roll that one die. (Plus an extra d6 if you're using an item or circumstances help you.)
But the way you frame it makes me feel like you'd "increase" the die size for each relevant Skill and Trait. For example, you start with a d6, but your Skill is a d10, so your baseline die for this roll is now a d10. But then say you also have a relevant Trait at a d8....the language of "increase" makes me think I would apply a +1 step up of my die to now become a d12. (As in, a d8 is a +1 step increase, a d10 is +2 steps increased, a d12 is +3 steps increased.)
So, to me the way it reads is your Skill gets you to a d10, and then a d8 Trait would increase you up one more step to a d12.
Is that the intention? Or are you supposed to roll a d10 and a d8 together?