Union of multiple columns as one column

I think can be achieved with multiple consolidation ranges for a PivotTable. Would need labels for the columns and more than one column per sheet (could clone the existing ones). Should sort and remove duplicates from the list automatically (if cloned).

EDIT:

I'll assume your IDs are all numeric (otherwise, sorting would be very tricky if not impossible without VBA). You could modify the following array formula to meet your needs (select an area with enough rows to hold the full stack of IDs, enter the formula, then commit the formula with ctrl+shift+enter):

=SMALL(IFERROR(CHOOSE(COLUMN(INDIRECT("C1:C12",FALSE)),Sheet1!A1:A73,Sheet2!A1:A70,Sheet3!A1:A79,Sheet4!A1:A58,Sheet5!A1:A51,Sheet6!A1:A94,Sheet7!A1:A50,Sheet8!A1:A89,Sheet9!A1:A75,Sheet10!A1:A89,Sheet11!A1:A70,Sheet12!A1:A94),FALSE),ROW(INDIRECT("1:"&COUNT(Sheet1!A1:A73,Sheet2!A1:A70,Sheet3!A1:A79,Sheet4!A1:A58,Sheet5!A1:A51,Sheet6!A1:A94,Sheet7!A1:A50,Sheet8!A1:A89,Sheet9!A1:A75,Sheet10!A1:A89,Sheet11!A1:A70,Sheet12!A1:A94))))

I'll use a smaller version (2 columns) to explain how it works:

=SMALL(IFERROR(CHOOSE(COLUMN(A1:B1),A1:A73,C1:C70),FALSE),ROW(1:143))

First, COLUMN(A1:B1) returns a horizontal array of integers between 1 and 2. Passing this to the CHOOSE function with the two single-column ranges creates a single 73 x 2 array from both A1:A73 and C1:C70 (instead of creating a jagged array, the last three values of the second column will be filled in with #NA).

Wrap the result with IFERROR to convert the three #NA values to FALSE (otherwise, SMALL will return an error).

Next, ROW(1:143) returns a vertical array of integers between 1 and 143. Passing the 73 x 2 array and the array of integers between 1 and 143 to SMALL will return a single 143 x 1 array (vertical) of the sorted values (the three FALSE values are ignored).

Note on INDIRECT: Using INDIRECT in this way makes the formula stable even if rows/columns are deleted; however, it also makes the formula volatile, which will cause it to be recalculated every time there is a change in the workbook, which could slow things down considerably. Another option is INDEX (e.g., ROW(A1:INDEX(A:A,COUNT(...))), which can be affected by row/column deletions, but isn't volatile.