Could the parts of a TAF that are relevant to planned time of departure or arrival as appropriate be emphasised in some way, say bold text perhaps?
I realise it could be quite a complex algorithm, but it would be useful in drawing the eye to the parts of the TAF that are relevant. An alternative approach might be to slightly dim or grey any parts which are likely to be irrelevant.
A further refinement could be apply the same logic to TAFs for airfields which are within a corridor either side of the route, with the deduced time of passage.