I have to agree with Mike, that there is a danger of overstating the uniqueness of Vadi's work. His individual plays are not unique, other than the eight at the very end of the manuscript, involving dagger and sword vs dagger, the first longsword technique, and two or three plays of zogho stretto. His opening chapters actually detail a lot of Fiore's plays that he DOESN'T show (for example, he describes how to perform the scambiar di punta, colpo di villano and the punta corta).
The main evolutions, IMO, are:
1. the stripping down of the armoured weapon systems, and renaming of the guards he maintains.
2. the addition of a different spear guard, that at first blush looks like tutta porta di ferro adapted to a longer spear. It is actually comparable an invitation position/lowline parry found in the Bolognese (but look at the grip of the rear hand - the spear can be used to thrust overhand or to cast one-handed!).
3. A reorganization of the sword guards to focus on point forward positions, with the right foot leading, and renaming therein.
4. An expansion of the segno, in part to explain his "new footwork".
5. An emphasis on initiating attacks with an acressimento and recovery with either a discressimento or pass.
Points 3 - 4 *are* significant, and make an interesting comparisons to Bolognese spadone, especially since Vadi's sword is fairly large. But, although back in 2002 I wrote in my book that he advocated an attack on a demi-lunge, and I stand by that, this "acressimento" is already covered by Fiore, and there are times that he uses the same. (See, for example, his discussion of fighting from dente di zenghiaro.) The other reason it is important to note this is that, although Vadi prefers right leg forward guards on the right side, if we look at his advice on how to parry, it is designed to create the same crossing at zogho largo that Fiore shows: left foot forward.
So is anything "new". Yes, I think so, and it is interesting to work with, since the devil is in the details. Here are three main examples I can think of:
1.Working with his guard positions and applying his discussion of the tower, sun and wheel from the Uomo della Spada (allegorical figure), his use of posta di falcon and the adapted posta di donna lend themselves towards a fast mandritto made with the acressimento of the right foot (the sun) while the left remains firm (the tower). If you needs defend, you can swiftly retreat with a discressimento of the same foot (moving back around on the wheel). He DOES NOT discount the pass, as some suggest, which is why we have the wheel metaphor - we can reverse which foot is the tower and which the sun.
2. The emphasis on the narrow stance (see Mike's post above), and the advice to keep the legs "well-paired" - which I interpret as a narrower stance, and NOT profiled, as folks assume, but actually a bit more squared - allows one to cut from side to side in the cross simply by using volta stabile/weight shifts. This is what I believe Vadi means about cutting "from knee to bending knee. And this is better footwork than the stepping of our ancestors". He is talking about not needing to actually take a step to cut around, but rather using body position and weight shift. This works pretty well, especially with longer swords, and something similar seems (to me) to appear in Marozzo's strette plays with the spadone.
3. Example, despite the "parry a mandritto with the left foot forward" advice, if we apply Vadi's assumed new footwork, we'll generally end up in dei Liberi's crossing of stretto (right foot forward), which may be that is the reason that Vadi prefers to illustrate primarily those plays.
So I would say that by ditching coda longa and altering posta di donna, plus adding posta di falcon, Vadi is substituting how he comes into measure and initiates a mandritto - with an acressimento, not a pass, and has attempted to adapt his stance somewhat to change the speed in which he can strike around the sword in the bind. Conversely, some of his left side guards put the left foot forward, meaning that he would enter with the thrust with a *pass*, whereas Fiore advocated an acressimento. I think these changes and preferences create some interesting differences in "the approach" phase of the fight - playing in zogho largo. Certainly we've seen that in fencing here. But I do think they are differences of degree, not kind, so even if Vadi is your root text, you will still clearly be in the dei Liberi school, just as Meyer is distinct, but still truly part of the Liechtenauer family!