"a pi c d as a whole modifies another word or phrase.
a pi b pi c d = (a (b (c d)), and imho is valid. The middle pi phrases however are followed only by one word. The tail must still be two words."
No, the first pi is followed by at least four words: the next 'pi' phrase also follows it. And so on.
In the area of controversy, I have made my position clear (I hope): the preps can modify an NP and, even when doing so, can take their complement NP, but that they then require a 'pi', for clarity (some at least) if nothing else.
not sure draining a swamp is a case of 'weka', but then I have no alternative at the moment. This says that the draining takes place in the middle of the land, wherever that may be.
the next is clearly wrong -- but I would say it was all right with 'pi' before 'lon' (open to authoritative correction; the chain of inference here is long enough to hide some gaps) not sure about duplication for repeated periodic motion or oscillatory.
Next doesn't say quite the same thing, now it's the rippling that is in the middle of the land, not the lake (although, of course, you need the lake there to ripple).
Nor the complementary comma to deal with other ambiguities.
Wrong -- the two-word rule. 'pi' is not a preposition (and preps don't have a two-word rule) so that doesn't help here. I'm afraid I don't see 'telo suli ma' as mud particularly (mo 'ko ma' or some such) That it refers to an aquifier is a better possibility. Not sure about 'kama ala' for "dries up" but seem to work once the nature of telo suli ma is established.
'ijo' isn't a placeholder particularly, though it may be handy when you can't think of the right word. In any case, the dummy isn't necessary, as the natural approach is to drop the 'pi' to achieve the same reference.
I'm not clear about the status of 'pi' as a verb. It seems tied to the notion of 'pi' as a possession marker (so not really a function word) and that seems to have died out early on. But I may be wrong about a lot of this, since there has been nothing definitive for several years.
[A quick check shows that as of a year ago, Sonja was still contemplating preps without 'pi' in NPs and even preferring preps to 'pi'. But these seem to be old notes only slightly revised in 2009, since they still have DOs in NPs and that has been pretty clearly out for ages. So, I don't know where things stand officially -- but you knew that.]