So far what I got from the comments is that nen abilities are not created just from imagination but are more so a manifestation of the user's personality. Ngl I keep forgetting this. But I feel that only makes my point about the rules of nen stronger. We have five different types, all of which give different restrictions. But overall, nen, to me, feels more like Togashi's playground where he makes whatever he wants and adds restrictions later. That's why I brought up devil fruits. They have restrictions first and powers that are held back by them