Sharepoint Document Library- Metadata

I don't think that's gonna work if you later want to show/query all the fields (like in a List View). From my experience, once I tried to add like 14 metadata columns to the Pages library. I was able to add them, but then I got errors when trying to show and item with all the columns (don't remember exactly the case, but didn't work).

Metadata columns are threated like "lookup" columns, and there's a limit here:

https://technet.microsoft.com/en-us/library/cc262787.aspx?f=255&MSPPError=-2147217396#Column

List view lookup threshold

12 join operations per query

Specifies the maximum number of joins allowed per query, such as those based on lookup, person/group, or workflow status columns. If the query uses more than eight joins, the operation is blocked. This does not apply to single item operations. When using the maximal view via the object model (by not specifying any view fields), SharePoint will return up to the first 12 lookups.

Note: After applying the SharePoint Server 2013 cumulative update package released on August 13, 2013 (https://support.microsoft.com/en-us/kb/2817616), the default value is increased from 8 to 12.