[QUOTE=roy]I suppose this would lead to dense negatives if the picture were to be made too complicated.

Roy,

The negatives you would produce would be just normal densities, if such a thing exists. Dense negatives are the result of overexposure and/or over development but adding elements into a still life subject part the way through the exposure cycle will not result in over exposure for you do not change the exposure that you had decided on at the start.