I was about post this in Ubercart to see you people are moving here :)

Say a Desktop PC processor has this long set of tech. specs. How could you create a module or something that, the datasheet item names and values can be used as a 'library' and subsets of it can be linked with various items. Example two processor models may have same set of tech. spec list but the feature values could be different. So having not them added allover again, you could first check the feature item for the datasheet and either use 'default' value or a 'custom' value for the features. Also, how could you 'expose' the top feature items from a datasheet, that the users would be search items by 'features. Something like you would see on many ecom. sites, the left side shows filters like 'Processor speed', 'memory unit(DDR2/3)' etc etc.

The datasheet would be like an 'independent library' that when a item listing expired and same item created again, the corresponding feature subset could be relinked based on it's SKU, whereas subsets of the 'datasheet library' could be saved 'Datatsheet nodes' named as a SKU value.

UberCart Feature API certainly won't be able to do it.