I have found this to be a huge missing piece of any SRSs I've come across. Personally, I have a pipeline that looks at what knowledge I've already learned and only then reveals successive information.

For example, I'm learning numbers in Spanish. First, I ask myself to go from doce => 12; then, 12 => doce. Then, once I have a few numbers in my memory, I can start to combine those into diez + dos = ? (answer doce). The idea is that this last example requires recalling three previously-learned Spanish numbers to arrive at the answer. This is a trivial example but this underlying structure of successive layers of knowledge shows up everywhere and is horribly under-exploited by our current learning systems.

Programmatically this can be done. Manually, this stuff takes way too much work.