I suggest allowing Necropolises to collect crystals. And also allowing them to be trained in universities, etc. Since even spacing is allowed and speeding up Necropolises is permitted, this would also be logical. Besides, it doesn't lead to any significant advantages, and I wouldn't say that it makes the game much more enjoyable. But in the early stages of the game, a couple of crystals consumed by a Necropolis can be very useful in battles (for example, when there is a critical shortage of armor).
That's it. If this is not possible, please provide a reasoned explanation as to why.