SQL Schema Change; Modification of Existing Table vs Creation of New
If your changes are not frequent and your parent table does not have a lot of data, then you could just update your schema on that table.  

However, potential downsides are changes in the schema could propagate to changes in stored procedures and views.  This could be because of adding columns or removing columns. 

(Of course, any change made in a database schema, will have some ripple effects that must be coped with.)

I like the parent table to be as stabile as possible.  Having a related table or tables to provide new requirements is a good general rule according to how I look at schemas. 

But it is definitely an opinion-based choice that will depend on what you are most comfortable with doing.