we know that a threshold is needed for a ward but does a better threshold make for a better ward? would using a great +4 reduce the complexity by 4? could i tag the threshold? or is it just a pre-req?
A threshold is *not* needed for a ward. Harry's house has no threshold (it's a rental), but does have a ward. Generally, you need some sort of
boundary to anchor a ward to, and that boundary can be something as ephemeral as a circle drawn with salt. Of course, a threshold would certainly do as a form of boundary.
As to the question about the impact of an existing threshold on putting up a ward ... well, I think that the existence of the threshold would certainly be worthy of some form of declaration, thus boosting the power level of the ward, or making the ward easier.quicker to put in place.