Typically, in infrastrcture and construction, entities are often specific sizes. When creating parametric content, it would be extremely helpful if variables could be controlled using value lists.

It is important that these are controllable independently, so Item Types do not provide a suitable alternative. To control variables indepently of each other would require Item Types of all combinations to work properly (A x A x A, A x A x B, A x B x C, etc). A simple solution would be to allow each variable to be controlled by a list of allowable values, meaning the user could select the required combination at placement.