...If it would be really inefficient, then i would like to try to come up with faster and easier way to do it, and if i could not, maybe i would reconsider pushing for the mix spinners...
Well I gave up on that matter anyways, but if we talk about efficiency - what exactly is inefficient about having two values displayed at the same time visible at a glance vs. having to click several times in order to get the same information (not mentioning the time it takes to create two nested maps plus getting an overview with older files). Now repeat the same x 10 for tweaking a value and re-rendering and you may finally understand where my definition of an efficient UI comes from.
I've already posted video some time ago showing it's not much slower or harder to do so. Those spinners may make this quite specific task simpler, but since it's quite specific task, it doesn't justify those spinners. There are dozens of other specific tasks you may want to do along the way with AO, such as clamp it to get crisp dents on edges, multiply it with other texture, randomize it's colors and so on, yet not even Vray Dirt has color mapping curve, built in multiply function or color randomizer. If it would, it would grow into crazy panel of buttons.
It's your workflow, and i respect that, everyone has their workflows, but if everyone's workflow was accommodated inside every single map, it would be a crazy software to use. What you request is doable, and it's doable without that much of an effort. But again, i do not know practical examples of your workflow. And i would love to get to know it, as i have quite bit of experience with shading, it would be a fun challenge to develop a workflow that would be both quick and efficient for your specific requirements. And if i would fail, it would definitely convince me we need those mix spinners.
BTW i get that you are used to Brazil where one could control literally everything. Render settings, materials and maps had just so many options. But that may also be one of the reasons Brazil ended up the way it did ;)