Basically give a column towards the wordpress_posts table in wordpress may i've problems in upgrade of wordpress??
Worpdress supports several systems for plug ins to store information in the database
- Store site wide options
- Store Publish Meta
- Custom tables
The content Creating Tables with Plugins mentions a dbDelta function that's employed for upgrading tables. The discussion concentrates on the way the function may be used to upgrade versions of custom tables but it is most likely employed for the upgrade of wordpress itself.
Due to this, adding a column to wordpress_posts will most likely not result in a problem for upgrades but could cause trouble for the upgrade but most likely would remove your column! I'd recommend using among the possibilities.