Changing custom table field's data type from DEC to CHAR

Hello,

My requirement is that the end user wants to able to differentiate between 0 and blank for a particular field.

The field of type DEC, and as a result both null and 0 values are always being stored as 0.00.

I am considering changing this custom table's non-key field from DEC to CHAR. [no foreign key dependencies]

I will activate and adjust this table in SE14, with "Save" option.

This table is being used in around 10 custom remote-enabled function modules.

What are the problems that could arise with this change?

What kind of impact analysis and tests do I need to perform?

Thanks and Regards,

Kavya