Summary
Instead of just Select and Boolean
Consider other attributes (text, string, date) valid to be enabled as Configurable Attributes (as Boolean plus metadata).

Example
Take for example the type "String".
Would be nice if can be enabled to let the user specify a text (note, customization) on each cart row.
As it is considered "Boolean" can also be used to change price in case the text is filled or not filled.

For a similar behavior you can check Opencart product options: http://docs.opencart.com/en-gb/catalog/option/