Hi Andrea
I finally have some spare time, and will try to answer the questions.
It is actually possible to combine anticipated and unanticipated conditioning (and exogenising as well, for that matter -- everything can be actually combined together in one run). Let me quickly code up a very basic example how to do this, and I'll email that to you in say 45 minutes. The basic idea is that you can assign std deviations of model shocks complex numbers, effectively thus introducing two shocks in the stead of each one -- an anticipated and an unanticipated.
Now, the "anticipation" and "unanticipation" describes the nature of the underlying shocks, and hence not necessarily the anticipation or unanticipation of the imposed endogenous variables. This closely relates to the other question about the partitioning of the structural shocks into disjoint subsets. I have actually given a lots of thoughts to exactly this question in the past, but haven't been able to come up with a satisfactory solution/design. I simply don't know if it's possible to do that in a simultaneous system... This question is, of course, independent of the anticipate/unanticipate issue, so let's say we have a static system with 2 variables (x,y) being determined by 4 shocks (a,b,c,d) -- think of it as a reduced form solution of a structural model
x = a + b + c + d;
y = 2*a - 3*b + 13*c - 5*d;
(the coefficients are totally irrelevant, of course:))
Whenever we use shocks a,b to condition x upon a particular value, this will automatically also change the conditional distribution for y, and hence influence the conditional distribution of c,d in case we use them to further condition y upon another particular value in the system. If we, on the other hand, do not condition x but we do y, then the conditional characteristics of the system with only y conditioned upon the same value as before will be different. In this sense, I don't see any possibility to construct disjoint sets...
Maybe there's a clever/simply way out of the simultaneity problem but I haven't arrived at it (yet?) :)).
Your thoughts are more than welcome.
M.