You could use reactors to re-build your model or have an 'update model' button to make the changes. It depends on how often you change your model I guess but a change is a change and should be deliberate.
Say you have your grids and they have a link to the members 'attached' to them some how, to change your model, move the grid/construction lines and hit the 'update model' button and watch it re-model using the stored modelling data for each part.