Actually I am not sure at all, but I guess this limitation is caused by the facelet compiler, that needs to resolve component IDs without having a request context. Do you know, whether the specs permit ValueExpressions as IDs? I do not think so.
Regarding your datatable problem: In general component IDs are not bound to model attributes, because user interactions are bound to components and not directly to the model. If your datamodel item type contains the appropriate fields for the select one, their should be no need for manually created IDs.
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