Yes, I know about the shredderand the equivalent Warp Spider spinners et al. It really depends on what you want to go for, the variety, whether you use purely Eldar weapons and Harlequins, or whether they would utilize Dark Eldar weaponry. It would only be for game balance reasons to give them a long range weapon capable of damage, or you could use the Shadow weaver support platform weapon rules (if used one handed, Night Spinner if two are used? Though that does remind me more of a Warp Spider styled Wraithlord ha haa).
The one thing having looked through the list but not playtested it that I can see is the severe lack of ranged shooting. That with the fact that you are against using War Walkers which in my opinion is quite rightly so (althought Harlequins used to be able to Rogue Trader era, there was even a model for it in the back of my first ever White Dwarr), I think it could be a problem that could be quite rightly adressed by giving the Marionette the 'option' to take longer ranged or indeed 'support style weapons. I don't think this would un balance the army in any way, as the Tau for example are a heavily shooting oriented army which still include a unit which is 'sufficient' at close combat whilst not rivalling the power of a specialised close combat unit such as Khorne Beserkers. The choice would be down to the player whether he wanted to make it a shooting or C.C. style unit, which when looking at the rest of the army is a nice 'break' from the C.C./pistol ranged weaponry. Above all remember these are just comments and sugestions to help make a potentially awesome codex, and the more that are put forth, the more you will get out of it. Which is'nt to say the work is bad in any way shape or form
That being said, as a side note I would like to ask you if it would be possible to use your codex on my site, if I could be so bold? Please feel free to PM me as i would love to hear from you and use something of this quality which will in turn hopefully be used by a lot of gamers.