Is there any concern with laying ABS drainline directly on the ground throughout the crawlspace. Other than possible grade issues.
Not sure what you are asking; As for the ABS making contact with the soil no it is buried on a regular basis. just lying on the ground with no supports the proballity of draining properly would be nil.
I am visualizing from your pic’s;-) a very poorly crafted installation
I don’t think it would be a problem if it had the minimum required slope of 1/4" per foot to allow for proper drainage.
The only problem i can see is that it would be hard to crawl over for future repairs etc…also a good place for spiders and snakes to hide…just not a very clean look either and not very professional which would lead me to look for other problems. It would be functional though…