This is just a current personal belief, and im sure its probably obvious to most of you, but id love feedback on it. (sorry if its been mentioned before)

From what ive read and understand the backbone to nearly all WILD techniques is concentration. Its concentrating on the movement of fingers for example that seems to have made FILD successful, or concentrating on counting in some other techniques. It seems that to concentrate and focus the mind, we can avoid being caught up in HI, we can maintain awareness even as our body begins to sleep.

Feeling very tired detracts from our concentration skills, just look at WBTB. We wake up early but lack some concentration due to tiredness, so we stay awake for 30 mins or so and then go back to bed, we are in a prime position to fall straight back into REM sleep but also have the concentration to maintain some awareness.
Even dream yoga seems to be based around the same principle to a certain degree, yogi's concentrate on visualisations while falling asleep to hold awareness.

The point of this post then:
Just as performing bench presses slowly allows us to do more pressups (because they work the same muscles), so should concentration excercises help us to achieve WILD. If we focus on and build up the foundation skill, we can expect a much higher degree of success when we attempt techniques requiring that skill.... in theory.

I intend to do more research on this to see the impact on WILD, Im currently making an app that will shout out numbers to put you off counting in your head for example, the object being to focus on counting without being influenced by the audio. Theres also many other concentration excercises on the internet aswell as just being aware during the day.