Not having seen this suggested, I search greywater forum for it, and found next to nothing I would love to gear you opinion of it.
seems like a natural, yet I can see wanting more small bits of carbon than a hugel normally has.
If seed with a hand sink->urinal like I mentioned in another thread, It could do a lot to alleviate any nitrogen suck that the wood might bring.
Logs at the bottom of a grey water mulch pit is interesting. In his book, Art Ludwig mentions that you want to use material that won't break down so easily. I wonder if that would work.
I guess you are not talking about a mulch pit though, just a regular hugel with a pipe sticking in it.
What did you end up doing?
You would be much easier to understand if you took that bucket off of your head. And that goes for the tiny ad too!