Issue with merging (or union) multiple "copy column" transformations - sql-server

Question

I have a legacy database that I am doing some ETL work on. I have columns in the old table that are conditionally mapped to columns in my new table. The conditions are based on an associated column (a column in the same table that represents the shape of an object, we can call that column SHAPE). For example:
Column dB4D is mapped to column:
B4 if SHAPE=5
B3 if SHAPE=1
X if SHAPE=10
or else Y
I am using a condition to split the table based on SHAPE, then I am using 10-15 "copy column" transformations to take the old column (dB4D) and map it to the new column (B4, B3, X, etc).
Some of these columns "overlap". For example, I have multiple legacy columns (dB4D, dB3D, dB2D, dB1D, dC1D, dC2D, etc) and multiple new columns (A, B, C, D, etc). In one of the "copy columns" (which are broken up by SHAPE) I could have something like:
If SHAPE=10
+--------------+--------------+
| Input Column | Output Alias |
+--------------+--------------+
| dB4D | B |
+--------------+--------------+
If SHAPE=5
+--------------+--------------+
| Input Column | Output Alias |
+--------------+--------------+
| dB4D | C |
+--------------+--------------+
I need to now bring these all together into one final staging table (or "destination"). Not two rows will have the same size, so there is no conflict. But I need to map dB4D (and other columns) to different new columns based on a value in another column. I have tried to merge them but can't merge multiple data sources. I have tried to join them but not all columns (or output aliases) would show up in the destination. Can anyone recommended how to resolve this issue?
Here is the current design that may help:

Answer 1

As inputs to your data flow, you have a set of columns dB4D, dB3D, dB2D, etc.
Your destination will only have column names that do not exist in your source data.
Based on the Shape column, you'll project the dB columns into different mappings for your target table.
If the the Conditional Split logic makes sense as you have it, don't try and Union All it back together. Instead, just wire up 8 OLE DB Destinations. You'll probably have to change them from the "fast load" option to the table name option. This means it will perform singleton inserts so hopefully the data volumes won't be an issue. If they are, then create 8 staging table that you do use the "Fast Load" option for and then have a successor task to your Data Flow to perform set based inserts into the final table.
The challenge you'll run into with the Union All component is that if you make any changes to the source, the Union All rarely picks up on the change (the column changed from varchar to int, sorry!).