I think that some instrument flight appreciation could only be a good idea for microlight pilots. The latest generation of microlights and LSAs are so capable as touring machines that pilots are often more likely to press on than risk damaging £70,000 worth of aeroplane trying to put it down in a field.
The downside would be the large increase in the cost of getting your license should it be added to the syllabus, as the aircraft would need to be fully equipped for instrument flight and thats going to cost.
Perhaps the LAA could do/already does an instrument flight appreciation hour or two through their coaching scheme?