I just came back from vacation and see this long thread about LPEs. I think I'm with Bulia on all points (but perhaps I missed something).
Before changing anything, I advice to thoroughly look through the current LPE code and understand it all. I think it is safe to say that nobody knows all about LPE anymore (in any case, its original author lost track of all the intricate details quite a while ago). All the different desired LPEs and use cases make for a pretty large set of details that have to be sorted out. I like the representation that we have now: it is human readable, concise and not overly verbose, and very closely follows the LPE design we had in mind.
(btw, have a look at SVG vector effects (svg1.2 i think), if you want more flexibility)
Cheers, Johan